Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A book good enough to have a permanent place on my shelves.

Fascinating study of the psychopathic (now called sociopathic) personality. Well written in a style that's easy to read. Many case studies, some funny, most tragic, of people who behave as though they grew up on Mars! The title refers to the fact that these people wear a "mask of sanity," but are in fact insane. Or at least, unsane. I recommend the book highly.