If this book has been subtitled `Know your own faults, and life will improve', and if it had stuck with the first eleven chapters, it would have been an excellent read.
Unfortunately, the actual subtitle is `The secret to making troubled relationships work'. To fulfil this promise, the subsequent eighteen chapters are filled with formulae and `five secrets' and tricks of behaviour that you're supposed to rehearse and role-play.
I'm not at all sure that these latter chapters will do much for troubled relationships. For one thing, the book seems to assume that the pain in the relationship will manifest itself verbally. That is, your partner will open his/her mouth at some point and say "You're putting my husband down", or "You never listen to me" or "Nothing turns you on!" or some other set of words that will usefully expose the heart of the problem. Perhaps this is a cultural thing, and perhaps people in the US are more likely to get into robust dialogues than us reticent Brits, but it seems to me that troubled relationships tend to get wedged in spaces where all communication carefully avoids the hot spots, or where the problem is acted out, or where sarcasm takes the place of honest complaint. And many people are completely unable to recognise their own emotions, never mind articulate those emotions in a useful way. In other words, there is no useful dialogue.
However, if that first dialogue ignition doesn't happen, then the rest of this book is just so much paper. There IS a chapter near the end that suggests that if the `five secrets' aren't working for you, it's down to YOUR failure to implement them properly. The possibility that there is nothing to implement them ON, does not seem to occur.
Even assuming that your partner in relationship angst does manage to come out with a helpful "You're a jerk" remark - which means that you can at least get your teeth into the problem - there's a further assumption that the partner's complaint against you holds a grain of truth (at least as far as they're concerned), and that acknowledging that truth will make the complainer feel relieved and `heard', and all will be rosy. While this may well be valid in many situations, there are an awful lot of other relationship dynamics - gaslighting comes to mind - where the 'grain of truth' is a weapon rather than a plea, and where acknowledging it is neither a wise nor effective strategy.
In all, this book comes across as being written by someone who spends an awful lot of time theorising, and not much time gathering information about real people in real relationships.
Read it for the first eleven chapters.