This is a very helpful, do-it-yourself physical therapy book. I suffer from frequent tension headaches, and the exercises in this book have definitely helped with that. I'm also currently going to physical therapy for a hip/leg issue, and the Brill exercises are very similar or the same as some of the ones I'm doing in PT. Instant Relief also contains clear explanations of what the exercises are accomplishing anatomically, what the potential issues are that they are remedying, as well as what such problems could evolve into if not addressed (e.g., arthritis).
This book is definitely worth owning and storing on one's frequently referenced shelf.