I’ve never read the Halo books, but now I really want to read them to understand the Halo universe. If you forum members could list me the Halo books in the proper order, that would be great 
- Fall of Reach takes place over several years, explaining the back story of the Spartans but it essentially starts “the end of the war” by showing Reach fall and then the following books continue to lead up past Halo 2, 3 and eventually 4.
Fall of Reach
The Flood (although it’s just the novelization of Halo Combat Evolved)
First Strike
Ghosts of Onyx
Glasslands
The Thursday War
- These two books take place at the start of the Covenant war and fill in some background information for characters like Sergeant Johnson, Captain Keyes and Thel 'Vadam (The Arbiter).
Contact Harvest
The Cole Protocol
- These two books take place 100,000 years before everything, detailing the Forerunner-Flood War and how these events will eventually lead into Halo 4.
Cryptum
Primordium