This has been one of the best self help books I've read and I love self help books. If you find yourself harboring unforgiveness towards anyone then definitely read this book. I definitely felt conflicted and convicted while reading this and I think it took me awhile to get through because I was working through an offense I had been holding onto.
In this book you learn that offense leads to bitterness and hatred and eventually worse acts. As Christians we are supposed to forgive like Jesus, which is hard because we let things get in the way. In the end of the book (I also read and worked through the journal) you have to forgive the people who you were upset at, it's very freeing.
Though that doesn't mean they will suddenly be perfect. This book acknowledges that and also how to reconcile with someone you've offended. Really great stuff!