I think it was the second book, but my fav part of them all was when dude was in the boat after they landed on Halo with active cam on, just sitting on the end like nobody say him, so commander boy asks for a gun, and just aims and blows dude away. In the book it says his parts were floating about or something, my memory fails me but it was great how they told that.
It was captain Keyes that did that, and that novel got some negative reviews so that's why there weren't any other novels based on the games.