The book is written in a pretty informal way, the author seems to talk to his son or someone really close, which I don’t really mind but, from my point of view, adds extra literature not necessary at all to explain the PSP.
The author focuses in two aspects along the book, measuring / planning and defects. The most valuable part and which I found more interesting is the one dealing with personal planning since it can help you not only when dealing with software projects but in your real life.
I really think that applying techniques such as registering tasks durations, interruptions management and creating week summary can help you become more productive and eliminate those periods of the day you think you are working but your not.
I also agree with the author that using his techniques you can become more realistic when planning a new project I think it is not because of the whole planning stuff but you can know exactly how many time are you really working in your projects without all that bloat of interruptions.
The part I don’t really like is the second half of the book which focuses in dealing with defects. The author ideas are only applicable when dealing with beginners defects and I don’t find useful any of the metrics he proposes.
In few words, this books is worth reading if you feel you are wasting your time and want to become more productive and/or want to make sure you can make realistic project plans.