Was the Halo books based off of the Halo game?

The books are based of the game (says in the back of the book) lol

Their mostly for true halo fans that give them tons of back story of the characters in halo

Example: you learn how John (aka Master Chief) came to be. fall of reach is before halo 1, the flood is halo 1, first cotact between halo 1 and halo 2, ghosts of onyx im not sure, contact harvest before halo 1 and just before halo wars, cole protocall i havent read yet.