- last post: 01.01.0001 12:00 AM PDT
The books are, as mentioned, official, and while they offer very different pieces of the story (with the exception of The Flood, which takes place through Halo 1), they are the same saga, without a doubt.
In addition to all that has previously been mentioned, there are the names and histories of the other living Spartans, an introduction to the Engineers (which didn't make it into Halo 2, although they were supposed to, according to the SE bonus material), and the fact that at the end of the last book, the Covenant was headed right for Earth. No shock to readers, Halo 2 starts with the arrival of the Covenant at Earth. I had never followed any pre-game release info, and yet I knew that would be the case, because of the books.
There is not a single contradiction between the books and the game stories that I've heard. They are continuous (or overlapping). They're not side stories, they're a prequel, a game novelisation and a sequel (or a pre-sequel to H2), in that order.