As neurosciences have advanced rapidly over the past few decades, technologies have developed in parallel. Of course tools affecting mental performance could be used for good or evil, and the author explores this thorougly. He reviews some basic principles, such as "entrainment", and then critiques some of the devices which exploit these prinicples. Out of curiousity, I purchased the Sirrius wave generating machine, and found it to be much as the author describes. Using patterned sounds and flashing lights, the device can entrain the brain into certain "modes" (alertness, rest, etc). My experience has been that it is an effective sleep aid. (I am aware of placebo effect, but I still believe the device works).This book seems to meet with a lot of skepticism when I bring it up, which is fine, but I would also recommend readers to keep an open mind.