I'll keep this short:
The book helps one understand why people do the things they do, feel the way they feel.
I highly recommend this book to anyone wishing to learn more about themselves, and others, why we sometimes hang on to bad relationships, get stuck, how we can overcome our self-induced suffering, our perfectly human feelings we fall victims to, and become better people, with more self-confidence and self-understanding, and opening the door to happier lives spent with the right people.
Criticism: the author repeats herself a lot, which lengthens the book quite a bit. I'd overcome this by just breezing through it with a confidence that anything missed will be reiterated elsewhere, but I would fear this may make me miss something that is important and not reiterated elsewhere. (got that?)
In short, anyone suffering, struggling with what to do next, wondering if there's a way out, if there's a better life (relationship-wise), or just wishing to better understand one's feelings, this book is a must read. If you had to read just one book, take this one.