I first picked this book up about 20 years ago just to see what kind of a silly book would have a title like that, but after reading just a couple of pages I realized that it actually contained some wisdom. After reading a few more pages I decided to buy it, and I can honestly say that it's been the single most helpful book I've ever read in my life. I've probably read it a dozen times since then and it's the one book that's actually changed my life. For anyone willing to make the effort, these methods truly do work, and you can start feeling the benefits almost immediately.
One thing that may put off some readers is that it contains a few leftover 60's words like "groovy," but, if one can overlook that, the underlying message is valuable beyond words. Ken Keyes draws somewhat on Buddhist ideas and other philosophies (as he notes in the introduction), but only a genius could organize them into such a practical and usable system.