The series that starts with Ender's Game has a parallel series that starts with Ender's Shadow. The graph of the timeline is... well... complicated.
Does it make more sense if you read them in the order they were first published, or if you try to read them in the chronological order of the story?
Image Reference: Ender's Game (series)
As someone who has read every book I think the publishing order is the best order to read them in because it is the order the author added to the universe. They each build on everything published before them and if you read them in a different order you don't get the same build-up and sense of discovery you would get by having things you may have wondered about in earlier books be revealed in later ones.
The "official" answer from Orson Scott Card is:
in truth it doesn't matter, except that you should read Xenocide right before Children of the Mind, since they are really two halves of a single continuous story. In most of my books, I include all the information you need.
The Ender series contains three major arcs. These are, in publishing order: Ender series, the Shadow series, and The War of Gifts.
Normally, one would read in the publishing order, but you could read these arcs in any order. Ender's Game, Ender's Shadow, and The War of Gifts are parallel novels that take place at the same point in time, from different perspectives. Their arcs then diverge from that point, from those unique perspectives. In fact, you could certainly read in a more-or-less chronological fashion:
Ender's Game, The War of Gifts, Shadow series, Ender series.
The advantage of reading in a chronological order is that the direct sequels of Ender's game take place thousands of years in the future and are quite distant from Ender's game in terms of plot. When reading chronologically, the story evolves in a more fluid an direct way.
The books under each arc are as follows...
In general, the books assume that you've read everything previously released. The nomenclature also evolved throughout the series, and going out of publication order will lessen one's reading experience. This doesn't matter as much regarding the short stories, but should ideally be followed regarding the main books.
The below chart I made shows which books should be read before every other book.
It should be stressed that pretty much every book in the series has a wildly different tone and style. Liking (or disliking) one book doesn't mean you'll like or dislike a different one. If you find you don't like what you're reading just put it down and jump to a different section.
Ender's Game was the first book, and is by far the most famous. It's definitely the recommended place to begin reading. That said, Ender's Shadow and Earth Unawares can each function as a starting point on their own.
Speaker for the Dead trilogy
This is the original sequel to Ender's Game, though there is a 3,000 year time gap, and the books have a pretty different tone and cast of characters. The short story "Investment Counselor" can be read right after Speaker.
Shadow Saga
Ender's Shadow is a parallel novel to Ender's Game, and tells much of the same events from Bean's point of view. It can actually be read prior to Ender's Game, though it's better afterwards. Hegemon, Puppets, and Giant form a trilogy set on Earth following up on a lot of the characters from Ender's Game and Ender's Shadow. It's a geopolitical thriller like a big game of risk.
There are two open plot threads at the end of Shadow of the Giant. One of those is followed in Shadows in Flight, the other is addressed in Ender in Exile. Messenger and (upcoming) The Last Shadow follow up on both Shadows in Flight and Children of the Mind, while also mixing in some elements from Ender in Exile.
Ender in Exile
Ender in Exile is a very much expanded version and continuation of the last two chapters of Ender's Game. The book also wraps up and spoils some of the plot from Shadow of the Giant, so it is recommended you read that one first. There are a few short stories that overlap with Ender in Exile, but most of them are completely included inside the book itself and therefore not worth reading independently. The exception is "The Gold Bug", which has a long intro not included in the book. "Governor Wiggin" is a short story Card wrote several years later, which is set during the same time period of Exile and should be read afterwards.
Formic Wars
These six books are prequels and cover the first and second invasion. These are not written by Orson Scott Card, but by his friend and collaborator Aaron Johnston. (Card serves as more of an advisory role and helps work out the plot.) Johnston has said that he plans to write a third trilogy after the second is finished which will continue following the characters in those books.
Fleet School
This book follows a new character and is largely set in Battle School after the events of Ender's Game. It was written as a tie-in to a video game which never ended up happening, and thus it isn't very likely for Card to write more books with the character. Children of the Fleet also involves some plot elements from Shadow of the Hegemon and Ender in Exile, and so should only be read after those two books. It also has some minor worldbuilding elements from the Formic Wars books, but should be understandable without. The short story "Renegat" continues the character many years later, but should not be read until after Speaker for the Dead.
Short Stories
"The Polish Boy" and "Teacher's Pest" are about Ender's parents and should best be read after their characters get expanded in Shadow of the Hegemon. A War of Gifts and Ender's Stocking have some overlap, and are both Christmas stories. The remaining three can be read anywhere in any order, and just give some prequel backgrounds to three characters from Ender's Game.
Orson Scott Card's official answer (as of 2009, so not covering Formic Wars and Fleet School) is to pretty similar to this. He recommends publication order for the novels, but advises younger readers to push off reading the Speaker trilogy. He says to hold off on the short stories until after Ender's Game.
Full quote follows (in spoiler text cause this answer is already long and some devices truncate unopened spoiler text blocks.)
The "preferred order" depends on what you mean by "preferred," and who's doing the preferring.
There are two main story threads. One begins with Ender's Game, and proceeds to Ender in Exile (which overlaps with EG) and then on to Speaker for the Dead, Xenocide, and Children of the Mind.
The other story thread begins with Ender's Shadow (which is parallel to Ender's Game), and proceeds to Shadow of the Hegemon, Shadow Puppets, and Shadow of the Giant. Eventually the two threads come together with the book Shadows in Flight.
The short stories make things even more complicated. They should NOT be read in chronological order because even though many are prequels, they only take on their full significance if you have already read either EG or ES.
The Polish Boy and Theresa (in First Meetings) are the stories of Ender's parents - who they are and how they meet. Mazer in Prison (IGMS) is the story of Mazer Rackham's recruitment by Graff to be part of the training of the future commander of the fleeet.
The stories Cheater and Pretty Boy are the stories of Han Tzu (Hot Soup) and Bonzo Madrid when they were children on Earth, before going to Battle School.
Goldbug (standalone comic and IGMS story) takes place on the first world Ender goes to, where he discovers the hive queen. It slides into the middle of Ender in Exile ... somewhere ...
Investment Counselor (First Meetings) takes place after EG and Ender in Exile, and before Speaker for the Dead.
The story War of Gifts (a novella) takes place in the midst of Ender's Game - sort of a side story. It can stand alone. There is also an IGMS story called Ender's Stocking that overlaps with War of Gifts but focuses on a crucial time in Peter's life.
The stories A Young Man With Prospects and Ender in Flight are both part of Ender in Exile, so if you've read that novel, you've read those stories.
You can read the novels in the order of composition: Ender's Game, Speaker for the Dead, Xenocide, Children of the Mind, Ender's Shadow, Shadow of the Hegemon, Shadow Puppets, Shadow of the Giant, and Ender in Exile. (This poses the challenge for younger readers of the very talky, philosophical and adult Speaker, Xenocide, and Children of the Mind.)
You can read the novels as two separate threads in sequence. For younger readers, the best plan is to read Ender's Game and Ender's Shadow in any order, and then proceed through the Shadow books and then all the shorter works, saving Speaker, Xenocide, and Children of the Mind until you're older.
Or you can struggle to read them in chronological order of the story, as described above.
Then again, the Empire books, the Homecoming series, and the Alvin Maker books are absolutely in chronological order and are very clear. They have nothing to do with Ender Wiggin or Julian "Bean" Delphiki, but at least you know what order they're in!
I know, the question seemed to be focused on the written works, but I thought I may as well cover the comics too. The comics were made after the books were already written, and so the publication order doesn't really matter. For the Comics, I would go with a modified chronological order starting with Ender's Game. Note that Ender's Shadow arc isn't necessary for understanding any of the other comics.
2These are one-shots and can easily be skipped.
First, read "Ender's Game" - it's the core book and establishes the setting.
Then I'd read "Ender's Shadow", which covers the same period of time from alternate points of view.
After that, it really depends on which plot you want to follow. There are two trilogies, and they go in very different directions.
The Speaker trilogy (Speaker for the Dead, Xenocide, Children of the Mind):
follows Ender after he leaves Earth, and takes place in the far future. It tends to focus on "meaning of life and universe" topics.
The Shadow books:
stay in the "present" on Earth, following Bean, Peter, Valentine, and the other supporting characters, and explores the aftermath of "what happens when a bunch of teenagers save the world". These books are a bit more political and realistic.
The short stories tend to be snapshots in time, and aren't really necessary until you've become well and truly hooked.
For instance, "Investment Counselor" introduces you to Ender's AI, but it works perfectly well as a flashback instead of reading that in it's chronological order. War of Gifts is similar, in that it fills in history without advancing the plot.
I would recommend either reading them in the publish order, or reading the Ender's series books first followed by the Shadow series. It doesn't hurt to occasionally switch books to be chronological either, but in general, the published order is probably best. There are very few interactions between the two sets (Shadow and Ender), so the chronological order between sets doesn't really matter, beyond the first book of each (Ender's Game and Ender's Shadow)
Read them in published order, as stated earlier you will most likely miss out on the wonder of the series by reading them for the first time chronologically. If your hooked enough to finish them once then go back and read them chronologically! I'm on my THIRD read through and am reading them in publishing order again because I found that the story just feels better that way. Card's writing evolves in a subtle but still noticeable way as time goes on and if you truly enjoy the series it is definitely better to "feel" the evolution as the story progresses.
I love the Enders Game series and in reference to the novels, every time I suggest reading them, I tell people to stick to the timeline. Card admitted that when he wrote the original sequels, he was still young and inexperienced. If you read "Enders Game", then the "shadow" books through "Shadow of the Giant", then "Ender in Exile", then "Speaker for the Dead" and so forth, it makes for the best read in my opinion. Specifically because there are familiar characters in Ender in Exile that you would recognize only after reading the shadow books and technically "Ender in Exile" happens before the end of the original "Enders Game" book.
This perhaps could be a comment but it's also perhaps a little bigger than that so I will venture an answer -- an answer that is very deeply personal.
When I was a small kid I read a lot. Refugee like, really, I had basically no friends (and many enemies -- I still carry the physical and emotional scars thirty plus years later) among my peers. In mathematics, I was far ahead of them, in many other topics, I was just ahead enough to be bored witless in school but I digress. My computer and my books were much better. I literally read every book in the children section of the local library. Needless to say, most of them didn't make a deep impression. Some years after this binge reading, however, it surfaced that I read a good book among them. I was not even sure what it was about but it was very good.
So I went back and found the book just by recognizing the cover. That was Ender's Game. On this second, much deeper reading as a pre-teen it anchored me and gave me hope that I am not a freak and there might be others like me. There's no book like it. Now I have a teacher's degree and while I do not teach, I am one of the founders and constant funders of a very small school. The book is never far from my thoughts.
I did read the Speaker trilogy. Speaker for the Dead was OK-ish, Xenocide was weird and Children of the Mind I barely could finish. Card went off on a philosophy angle about, what, I do not even know what. It certainly doesn't resonate with me.
Almost ten years later Ender's Shadow came out. I actually liked it so much I tried to translate it to Hungarian so others can read it. I only got to the Anton chapter and couldn't continue, reading and re-reading that one was too much for me emotionally. But the book is very, very good and for me while Ender's Game told me there are others like me, Ender's Shadow showed that there are many others just as cruel as my peers were. It certainly helps atuning the young "all people are nice" attitude to the real world. It's brutal. But a dose of reality, even if very bitter, is helpful.
Another few years later I was the only European at EnderCon in Utah in 2002. I was not yet the world traveler I would later become, it was quite a big adventure for me.
I read the other Shadow books. They should've been called Shallow not Shadow. Frankly, I barely remember anything of them. I will admit not even bothering with the prequels.
My advice based on nearly thirty years of reading them and partially defining myself by them is this: read Ender's Game and Ender's Shadow. Most especially read them if you are a pre-teen (12-13) or a teenager. Forget the rest.
