About 20% in I almost gave up because the author sounded really full of himself.
Since that seems like a really inconvenient trait to have as a hostage negotiator, I hope that it's just the way the book is written.
That said, at the end he still sounded like an arrogant pompous boastful man, which wasn't helped by the constant reminder of what an excellent Christian he is. (I got that point the first few times, thanks.)
The end, where he describes how a few hostage situations went down, was really interesting though, so I'm glad I stuck with it.