Let me be completely up-front, here. I'm the author. So this is less of a review, and more me explaining my motivations and goals behind writing this book.
GURPS Fourth Edition added a ton of flexibility to psi. I mean, a lot -- the possibilities went from "a simple list of psychic abilities" to "anything you and your GM can agree on -- no, seriously, anything!" This freed up psi to fit any setting, but also overwhelmed a lot of people. GURPS Psionic Powers exists to harness that flexibility, and bring it back down to Earth in the form of a simple power system and a selection of 10 different psychic powers (e.g., ESP, Psychokinesis), each with a list of pre-made abilities. In many ways, it's the power and balance of Fourth Edition psi wrangled into the simple, easy-to-understand (and use!) framework of Third Edition psi. You can pick up this book and build a character without knowing a thing about power-building or detailed game mechanics -- it's as simple as, "I'll take Telesend at level 3, Suggestion at level 2, and Mental Stab at level 4," then buying the associated skills. I think it's the best of both worlds, and many readers have agreed.