I think you're looking for the Phenomena novels by Ruben Eliassen.
Phenomena is a series of Norwegian Young Adult fantasy books written by Ruben Eliassen. The series follows the elf boy Alk and his twin sister Ilke, which according to an old prophecy has the power to defeat Tarkan, the fürst of darkness, and by that free their world from his evil regime.
Possibly The Escape Orbit by James White (1965)
Here is a cover from the original 1965 Paperback
And the 1983 reissue which I remember
Basic plot is a galactic war between two factions
The War is between Humans and chlorine-breathing Bugs.
I have a memory of forests and maybe tree houses, with that sort of 'wood based' technology, if you see what I ...
Perhaps Mercedes Lackey's The Outstretched Shadow? It was published in 2003, which is a little out of range but close. From memory, and it's been a while since I've read the series myself:
The main character is the son of a (or The?) high mage, but struggles with the formal magic system.
He finds a book to teach him Wild Magic in the city market
He learns ...
That's Kristen Painter's House of Comarré series. There are 5 novels and a short story.
Copy from the first book, Blood Rights
Born into a life of secrets and service, Chrysabelle's body bears the telltale marks of a comarré—a special race of humans bred to feed vampire nobility. When her patron is murdered, she becomes the prime suspect, which sends ...
This may not be what you're thinking of, but as we don't have any details of the plot, this reminds me of a Magic Tree House book called Winter of the Ice Wizard:
Merlin the magician and Morgan le Fay have disappeared, and in order to find them, Jack and Annie journey with their friends Teddy and Kathleen to the Land-Behind-the-Clouds, a frozen kingdom of ...
This sounds to me like The Player of Games, by Iain Banks, published in 1988.
It is one of the best known of the author's Culture novels (which cover all sorts of different science fiction subgenres) and the second one he published. It has been published with a number of covers, but this seems to be the most common one.
The common setting of the Culture ...
This sounds like a segment from the 4th book of James Clemmens' The Banned and The Baished series. The series was published between 1999 and 2003.
The series is a five book epic centred around the journey of the Wit'ch from childhood innocent to fantasy epic hero with her surrounding band of support heroes freeing the land from the Tyranny of the big bad.
"A Maze of Death" by Philip K. Dick
Synopsis from Wikipedia:
The plot revolves around fourteen colonists of the planet Delmak-O.
They are: Betty Jo Berm, a linguist; elderly Bert Kostler, settlement
custodian; Maggie Walsh, a theologian; Ignatz Thugg, who oversees
thermoplastics; Milton Babble, a physician; Wade Frazer, a
psychologist; Tony ...
The first part of your question is pretty close to Star Rigger's Way (1978) by Jeffrey A. Carver. The ship itself isn't experimental, though, it's the situation that is unprecedented.
Quoting the Google books summary:
His shipmates dead, star rigger Gev Carlyle is adrift in the Flux, the subjective hyperspace that carries ships between the stars. His ...
Skeletons by Al Sarrantonio
In Moscow, the sound of bones echoes across Red Square. In America, skeletons patrol the streets of Manhattan and blood stains the confields of the Midwest. While in Washington, D. C., Abraham Lincoln is heading for his third term in the White House.
The best-and worst-of humanity are back with a vengenace, a skeletal army ...
Mr. Adam, a 1946 novel by Pat Frank, better known as the author of Alas, Babylon. The text is available at Faded Page. It's not an all-female world, but there's only one fertile man in the world, and his name is Homer Adam. Does any of these covers ring a bell?
Front cover blurb from a 1948 Pocket Books edition (image below):
Would you like to be the ...
This reminds me of Revenge of the Damned, one of the Sten series by Alan Cole and Chris Bunch. The story starts in a POW camp on a prison world. The enemy are the Tahn, human but not part of the Empire the Sten serves. Sten was recorded as a prisoner under another name ("Horace" something, don't recall the last name) because his friend Alex had switched ...
female engineer who uses 3 types of robots
In Neal Stephenson's Seveneves, Dinah MacQuarie is stationed on the International Space Station, and in charge of four types of robots: Grabbs, Siwis, Buckies, and Nats. The Siwis may be what you're referring to as a worm:
"The Siwi is adapted from a robot that was made for exploring
collapsed buildings. ...
This sounds like the Chasing the Valley trilogy by Skye Melki-Wegner that came out in 2013.
From the first book's page on Goodreads:
Danika is used to struggling for survival. But when the tyrannous king launches an attack to punish her city – echoing the alchemy bombs that killed Danika’s family – she risks her life in a daring escape over the city’s ...
The book A Touch of Magic by Gregory L. Mahan has many similarities to what you describe:
Magic is outlawed except by those under control of the king/elite
Main character found a book of magic
Main character meets/learns from imp
Main character in exile
Differences from what you describe include:
Recent - published in 2011
I don't recall ...
The Crystal Warriors by William R. Forstchen and Greg Morrison
From review on goodreads.com:
A group of American soldiers are being chased by some Japanese
soldiers somewhere in China during World War Two. They stumble across
an ancient temple, and both the Americans and the Japanese are pulled
through to another world.
This might be Pawn's Dream (1995) by Eric S. Nylund.
The Google Books blurb says:
Roland Pritchard's dreams of being in a monastery in a fantastic world offer him an escape from his lonely existence as a convenience store clerk, although the monk has dreams of his own, nightmares of a future world.
It appears as though the book had different covers in ...
This might be Into the Labyrinth (2002) by Roderick Townley.
The Amazon summary of the book mentions the story being changed around:
What a relief when the old storybook is republished and the characters who live inside it suddenly discover they have Readers again - lots of Readers - especially when the book is loaded on to the Web. The endless reading ...
Perhaps Legacy by James H. Schmitz. The lead character is Trigger Argee there are murders on a spaceship and I believe when Trigger sees the murderer briefly she thinks it's a big cat.
From the book:
Trigger said, "I thought that catassin planet was being guarded."
Turning someone else's comment into an answer.
Uprooted is a 2015 novel by Naomi Novik
Agnieszka loves her valley home, her quiet village, the forests and the bright shining river. But the corrupted Wood stands on the border, full of malevolent power, and its shadow lies over her life.
Her people rely on the cold, driven wizard known only as the ...
This series is The Seventh Tower by Garth Nix.
The Seventh Tower is a series of six books written by Garth Nix, the result of a joint partnership between Scholastic and LucasFilm. The series follows two children from distinctly different societies in a world blocked from the sun by a magical Veil which leaves the world in complete darkness.
Tal is a ...
This would seem to be Robota, a 2003 illustrated novel by Orson Scott Card with illustrations by Doug Chaing.
There is a picture of the cover that matches the OP's recollection very closely.
The summary from Amazon also fits the information supplied by the OP in the question.
Academy award winning artist Doug Chiang and best-selling sci-fi ...
While it is probably not the book you're looking for due to the year it was released in (1998), Echoes of Honor is the first book that came to my mind.
The protagonist's name is similar to the person you recall as a possible author (Honor Harrington ~ Henry Harrison); the main character (MC)'s death is heavily implied in the first chapters; the prisoners ...
This is a long shot. The astronaut Buzz Aldrin and the SF writer John Barnes co-wrote a science fiction novel published in 1996 called Encounter with Tiber a.k.a. The Tides of Tiber. Within that novel there is a story-within-a-story that describes the experiences of some advanced aliens who came to Earth nine thousand years ago.
It is a long time since I ...
Just taking a stab, could it be Starstruck by Brenda Hiatt?
Nerdy astronomy geek Marsha, M to her few friends, has never been anybody special. Orphaned as an infant and reluctantly raised by an overly-strict “aunt,” she’s not even sure who she is. M’s dream of someday escaping tiny Jewel, Indiana and making her mark in the world seems impossibly distant ...
I upvoted @cycad for suggesting Schmitz, but I believe that the story cited (Legacy or A Tale of Two Clocks) is the wrong Schmitz.
I believe the story is Schmitz's "Lion Loose". (Downloadable at Project Gutenberg.) The main character is Heslet Quillian (who Trigger Argee meets in A Tale of Two Clocks). The woman involved is probably Reetal Destone, a ...