I bought this book at the same time as "The Relate Guide to Separation". I'd describe the Relate book as a typical self-help guide: useful, but trite in places but with some helpful exercises, if you can be bothered.
"Uncoupling" on the other hand is a powerful, well-written treatise on the patterns behind break-ups. It is more academic than the Relate book (with numerous end-notes and references to other works), but it's comforting to realise that the emotional reactions (for example, the way we re-write our relationship's history, with the benefit of hindsight) are common to many other break-ups. It helped me understand what I'm going through.
And on top of that, I finally understood the value of sociology! I'll never mock again.