Half interesting, half very dry and occasionally boring. Richard Cytowic is obviously very interested in synaesthesia - what causes it, how it is manifested in different people, whether or not you can track it by scanning the brain etc. - but his book isn't really meant for non-medical readers. I was fascinated by the experiments and the discoveries, but there was a LOT of medical babble that I had no interest in at all, and ended up just skimming. A non-fiction that reads too much like a textbook for me to enjoy it as "casual reading".