What is the shortest route through the Horus Heresy series?

Question

I have begun reading the Horus Heresy stories in the recommended order:

1. Horus Rising
2. False Gods
3. Galaxy in Flames
4. Flight of the Eisenstein

I've also read Fulgrim where the story moves onto Isstan V and a few of the Thousand Sons/Space Wolves arcs.

I want to catch up with the most recent books however I'm daunted by the remaining 40+ novels in the way (at £9.99 each the entire series would cost about £500 to buy). I know that many of these cover other arcs such as the Ultramarines and Imperial Fists stories.

I want to read the books as they come out but I'm happy to leave the other arcs for the time being. Are there any books which are essential reading between the opening five and the newest one (at the time of writing #49 called Wolfsbane)?

Answer 1

Books of the Horus Heresy on Wikimedia, recommended books are highlighted:

_{Suggested books outlined in red}

It is very difficult to give you an answer on which books to read and which to skip as it's heavily dependant on what subject of the Horus Heresy interests you and what you consider essential knowledge. So, I'd heavily recommend you to check the synopsis on the books by yourself and consider if you think it's worth reading.

Some books that (IMHO) are essential to understand the Horus Heresy:

1. Horus Rising (Get an idea of Horus and how he ticks)
2. False Gods (The root of the Heresy and how Horus fell to Chaos)
3. Galaxy in Flames (Isstvan Dropsite Massacre, essential to understand later references)
4. The Flight of the Eisenstein (How the Imperium learnt of the Heresy and how they reacted)
5. Fulgrim (How Fulgrim fell to Chaos)
6. Legion: Secrets and lies (How Alpha Legion fell to Chaos and why they're considered loyal to the Imperium)
7. Mechanicum (How and why some part of the Mechanicum fell to Chaos)
8. A Thousand Sons: All is Dust (How Magnus was tricked into service by Chaos)
9. The First Heretic (How Lorgar fell to Chaos)
10. Prospero Burns (How the fate of the Thousand Sons was sealed)
11. Deliverance Lost (Raptor Project of Corvus Corax and how the Alpha Legion made sure it didn't succeed)
12. Unremembered Empire (Imperium Secundus and the base for the Codex Astartes)
13. Vengeful Spirit: The Battle for Molech (How Horus got the favour of Chaos and become their tool)
14. Eye of Terra - Aurelian: Novella about Aurelian, specially part two of it (The Pilgrim) describes how Lorgar Aurelian became the traitor Primarch.
15. Path of Heaven: What the White Scars had to endure and how they could go to Terra despite the Ruinstorm. Also gives more information about the Human Webway project.
16. Praetorian of Dorn: Terra is attacked by the Alpha Legion way ahead of Horus and how the Imperial Fists defend against it. (SPOILER, can't hide due to list: Alpharius dies in this books)
17. The Master of Mankind: The Emperor and Custodes try to defend the webway project of the emperor against Chaos. Explains why the Emperor did not play a more important role in the Horus Heresy and what his plan for mankind was, his motivation etc.

Can't yet give any more "required books" to understand the Heresy as I am not yet any further. I'll update as I keep reading.

Why I consider the other books not essential, I've left out the novels containing only short stories:

• Descent of Angels
  • Story of Lion El'Johnson being reunited with his legion
  • Interesting to understand the Lion but IMHO not essential to get the greater picture of the Horus Heresy
• Battle for the Abyss: My brother, my enemy
  • Story of a gigantic ship that attacks Ultramar but is stopped by Ultramarines
  • Interesting to know that the Mechanicum was involved in the Heresy very early but not essential to get the main storyline.
• Fallen Angels
  • Continues the story of Descent of Angels
  • Again interesting but not essential to get the important points during the Heresy
• Nemesis
  • Officio Assassinorum operatives try to kill Horus why a Chaos assassin tries to kill the emperor.
  • Has no effect on the story arc.
• The Outcast Dead
  • How legionairies of the traitors flee from a prison on Terra but are killed by a Thunder Warrior
  • No effect on the main story.
• Know No Fear: The battle of Calth
  • Word Bearers attack the planet of Calth and lay ruin upon it and summon the Ruinstorm.
  • Interesting to understand how the traitors fight and how the ruinstorm came to be. It's sufficient to know that the ruinstorm was created by the traitors to block the loyalists. It has some effect on the Ultramarines and basically is the source of Guilliman for the Codex Astartes but it's the fight for a single planet.
• Fear to Tread: The angel falls
  • Horus trying to bring the Blood Angels to his side.
  • Has some impact on the Blood Angels but not on the wider heresy.
• Angel Exterminatus: Flesh and iron
  • Fulgrim tries to attain daemonhood by sacrificing Perturabo
  • Interesting to get how Fulgrim became a Daemon Prince and how Perturabo ticks but not essential for the wider heresy.
• Betrayer
  • The attack of the Word Bearers and World Eaters on Ultramar and the summon of the Ruinstorm (that failed in Know No Fear).
  • It's sufficient to know that Roboute had no contact with the wider imperium and was not able to travel to the help of Terra, which is also explained in Unremembered Empire
• Vulkan Lives: Unto the Anvil
  • How Vulkan survives (he's a perpetual) and is tortured by Konrad Cruze
  • Interesting to know how Konrad ticks, how Vulkan survives but has no impact on the wider heresy.
• Scars: A Legion divided
  • About the White Scars and how they found out what happened on Proserpo. There is an internal fight between loyalist and traitor White Scars legionnaires and why they've decided to join the loyalists. But it's no turn point in the whole heresy.
• The Damnation of Pythos: Thinning the veil
  • Iron Hands, Raven Guard and Salamders land on a chaos infested planet and must try to survive.
  • Interesting to see what happens to a planet that's been infested by Chaos but has no impact on the wider heresy.
• Deathfire: Into the Ruinstorm
  • Salamanders bring back the corpse of the dead Vulkan to Nocturne for him to ressurect.
  • Interesting to get more of how the Salamanders tick and what they're willing to give to bring back Vulkan to Nocturne but no impact on the wider Heresy.
• Pharos
  • Fight over the planet Sotha, where the Pharos is located.
  • Interesting to learn about the Night Lords way of war but has no impact on the greater story.
  • At the end, there is a hint that Tyranids were waiting for something like that.
• Angels of Caliban: Emperors and slaves
  • Lion El'Johnson tries to find Konrad Curze and bring him to justice, basically destroying the trust of Sanguinius and Roboute into him.
  • Story how Caliban got infested by Chaos and why Luthor fell to chaos.
  • No real impact on the wider story.
• Corax
  • Coruvs Corax wages war against the traitors behind enemy lines.
  • It's sufficient to know that the Raven Guard were combating the traitors and weakening them, no impact on the wider story.
• Garro: Weapon of fate
  • Garro becomes a knight errant for Malcador and is tasked with different missions.
  • Bit of Sigismunds story is releaved as well as some background to the faith into the Emperor.
  • Not essential for the story but might be interesting to know how Malcador worked and to better understand "after the Heresy" lore.

Answer 2

Understand that the Horus Heresy series is not so much a single linear progression, but rather an intertwined set of books covering different events occurring during this era of Warhammer 40K lore.

What I've been doing to get through the series is:

1. Check out the core rulebooks and other fluff sources (e.g. Index Astartes entries) for the games. Fluff basically refers to any lore or background information on the game, as opposed to game rules. These sources are great general primers for the 40K universe, the history of the Imperium, and the Horus Heresy. Find topics that may interest you. Examples might include:

• The Great Crusade/years leading up to the Heresy
• The "Shattered Legions" (Space marine legions decimated at the onset of the Heresy)
• Nathaniel Garro
• The Mechanicum
• The Imperium Secundus

2. Look up those topics on Lexicanum. This is one of several Warhammer 40K wikis, and the one I find to be the most responsible as far as citing sources. This will give you a general overview of your selected topic, and basically list the books that feature significant events for said topic.

• For example, Lexicanum's entry for the Alpha Legion references Dan Abnett's Legion (Horus Heresy #7), so that's probably a great book to read if you want to learn more about those guys.

2a) Lexicanum is a great source to find new topics of interest as well. Rather than using the rulebooks as a starting point, you may find yourself simply meandering from page to page until you find something really neat and go from there.

3. Once you've found a book fitting your topic, give it a read. The basic info you've gathered previously should give you enough to figure out most of what's going on without having to read the entire novel series. If there is anything you're unsure of, head back to Lexicanum to fill in the gaps.

BONUS: While writing this, I came across a neat chart detailing the major story arcs during the series, which map out what novels and short stories to read, and in what order, to follow these arcs. It seems to be up to date as of the release of Master of Mankind in June 2017.

As Shade mentioned in their answer, a more up-to-date and interactive version of this chart is available here, which includes some of the newer series such as the Siege of Terra (outlining the last phase of the Horus Heresy).

Hope this helps. Happy reading!