In Relapse he gives a really candid and open look into his life. He discusses his struggle with addiction, the pain of losing family members, and this book reads like a conversation with a friend happening over hours and warm coffee.
His writing style is very easy to pick up and the book is short, so even if you are a very casual reader this is one to grab.
Unlike most books that reference addiction, his take isn't black/white on the subject. I think Relapse is remarkably non-judgmental. It is refreshing to read recovery as it is- tentative and hopeful, but never ever for granted.
I highly recommend this book.