Slightly spoilerish:
I read both books about 2 years ago. First season closely mirrored the book, which is told completely in the first person from Joe’s POV like the show was. The second book is a continuation of the same character (Joe) in a new setting with mostly new characters, but the old plot lines don’t disappear. It’s entertaining, and I enjoyed it, but it’s not very believable. In fact it’s much less believable than the first book.