You should read the other three first.
The Fall fo Reach-explains itself which also covers how MC became MC.
The Flood-The first Halo game with more detail of not only MC's story, but the other Humans and the Covenant.
First Strike-Between Halo 1 and Halo 2
Ghost's of Onyx is written by Eric Nylud (I think) who wrote The Fall of Reach and First Strike.
sweet, yeah i'll check them out. i dont like reading but have to read a book for school so it might as well intrest me.