Learned a lot about people in the MMA world who aren't named BJ Penn, and I can't say the portraits of them were too flattering. Now, this is only one side of the story, but regardless of how you feel about BJ, he does come across as honest. It was one of the better books by a fighter I've read yet, even though (or perhaps due to the fact that) it was coauthored.
Postscript: I heard today, 2/13/13, that BJ mentioned the dropping down to 155 and fighting as a lightweight once again. Only time will tell if this pans out, but I'll certainly be supporting the Hilo Kid whenever and wherever he fights!