I loved the books, they werent stupid stories based around a game, they really created a unique backstory for them that was for the mature reader. In fact I believe the stories they tell are accepted as fact, particularly since one covers the mysery of his return to earth in halo 2. (Stealing a covenant carrier and bringing it home)
The graphic novel I was not impressed by though, I did own it briefly bu after actually reading it, couldnt find reason to keep it. The artwork was disapointing and stories irrelevant to anything. Im still working my way through onyx and contact, I rarely get chance to lose myself in a book lately.