I’ve played Halo 1-4, but I’ve never read any of the books. I’ve noticed that people are saying alot of characters from the books are appearing in Halo 5, so my question is, what books should I read to maximize my Halo 5 experience? I don’t want to be playing through the campaign, and come across someone who’s supposed to be recognizable from the books, and not have a clue who they are.
Well first, you should read The Fall of Reach and First Strike to learn more about blue team’s origins and backstory. Next, you should read New Blood to learn more about Buck’s post-war actions and last, you should read the new book Hunters in the Dark that comes out next week because I hear Olympia Vale will play an important role in that novel. Hope this helps!
Halo: Fall of Reach and First strike
Truth be told, I don’t think any heavy reading is going to be absolutely necessary. The Game Informer article mentioned how the AI teammates will talk, and along with cut-scenes I think that will be sufficient. But Blue Team’s characters can be found in The Fall of Reach and First Strike. Ghosts of Onyx and Glasslands go a bit further, but their presence is somewhat minor in Glasslands. If you wait until September 7th Blue Team has a role in the digital book Last Light. Locke has no presence outside of Halo: Nightfall and the first few Halo 2 Anniversary terminals as far as I know. Holly Tanaka is introduced in Halo: Escalations #17 and #18. Olympia Vale apparently has a role in the book Hunter in the Dark set to release next week on June 16th. Buck should be familiar if you played Halo 3: ODST, but New Blood follows his journey in becoming a Spartan.
I recommend Fall of Reach and First Strike like many others before me. Nice backstory on the Spartans, but also really great literature. I think everything else you can get by through halopedia, though I’ve heard great things about the forerunner trilogy
Everyone else already stated Fall of Reach and First Strike for sure, as well as a few others, so read those, and I definitely recommend the Forerunner Trilogy: Cyrptum, Primordium, and Silentium. Those books teach you a lot about Forerunner history, several main Forerunner characters, how some of their technology works (and some tech we didn’t see in Halo 4 but may come up later), and you can learn about the Didact’s history. Good reads, pick 'em up
Even better, read all of the Halo books if you can/want to 
New Blood, Hunters in the Dark and Last Light are probably good bets.
I’m just regurgitating what everyone said, but Fall of Reach is essentially required reading. Everything else is optional, but does contain a lot of useful information. Though if you’re really interested in getting into the books let me put down some briefs for ya.
The Fall of Reach: As I said, required reading. This book released alongside Halo: Combat Evolved and follows the Master Chief from when he was first conscripted into the Spartan-II program all the way up until the end of the Battle of Reach and beginning of Halo: Combat Evolved. It also introduces Fred, Kelly, and Linda as well as many other Spartan-II’s including Samuel who is very important to all Spartan-II’s.
The Flood: This one can be skipped with no consequences. It’s a retelling of Halo: Combat Evolved with the only difference being the fleshing out of the Battle of Installation 04. Quite a few things that weren’t in the game are shown here.
First Strike: First Strike bridges the gap between Halo: Combat Evolved and Halo 2. It essentially explains how Chief and Johnson made it back home in one piece. And of course it brings Kelly, Linda, Fred, and Halsey into the fold again. Basically it’s the second half of Fall of Reach.
Ghosts of Onyx: Ghosts of Onyx is all about the Spartan-III Program and spans a good twenty some years ending pre-Halo 3. It also features Fred, Linda, Kelly, and Halsey, but doesn’t really add anything to anyones character other than Halsey.
Contact Harvest: This book is the story of the beginning of the Human-Covenant War and acts as sort of a backstory for Sergeant Johnson as well as setting the stage for Truth, Mercy, and Regret.
Glasslands: Ties up the plot left open by Ghosts of Onyx and shows the post-Human-Covenant War galaxy and introduces Jul 'Mdama if I’m not mistaken(Correct me if I’m wrong please.).
The Thursday War: Sequel to Glasslands, it continues to explore the post war era.
Mortal Dictata: Third verse same as the first two.
Cryptum: The first book in the Forerunner Saga. It introduces the Didact, the Librarian, Bornstellar, and many other interesting Forerunner characters, as well as establishes that Humanity and the Forerunners are not one in the same like Halo 3 originally hinted(aka a retcon.). This book, as with the rest of Forerunner Saga, will give you a better grasp of the Forerunners as well as better explain the Didact in Halo 4.
Primordium: The second Forerunner Saga novel and where -Yoink- starts to get really interesting.
Silentium: The third and final book of the Forerunner Saga. This book in particular sets up Halo 4’s conflict, the other two were just background, but important background nonetheless.
New Blood: Consider this book Halo: ODST 2. It follows the same group of characters except AFTER Halo 3: ODST. It acts as an extended epilogue to ODST where it explains what happens to the characters as well as setting up Buck for Halo 5: Guardians.
Hunters in the Dark: A book with joint UNSC and Sangheili forces. It also introduces us to Olympia Vale and brings Usze 'Taham(4th player character in Halo 3. Ya know, the red one.) back into the story.
As you can probably guess, I haven’t actually read the three Kilo-Five books(Glasslands, The Thursday War, and Mortal Dictata) and the Forerunner Saga(Cryptum, Primordium, and Silentium). However, I know enough about what happens in them to give the basic gists. Though I’ve often been told to completely avoid the Kilo-Five Trilogy.
I dare say you’ve already got the gist of what to read, but personally, I think the most important ones to read in terms of how they’ll affect the overall plot, would be the Forerunner trilogy by Greg Bear, followed by the Kilo-five trilogy by Karen Travis (mainly for the side-story in them so you could just search that online?).
Also, definitely read any books about Blue Team. The more you understand about them the more you’ll love the in-game interactions I feel.
None of this is essential, as that’s not 343’s way…but if you want to, there’s your reading list ^
~ Duck.
I strongly recommend you read the original Fall of Reach book and not the “Definite Edition” one, the definite edition still contradicts Ghosts of Onyx, due to the fact of Halsey being unaware of the Spartan III program. I wish they’d just said that Halo: Reach was alternate reality just to demonstrate what happened on Reach, the Canon wouldn’t be soo screwed.