"Don't judge this book by its cover" says Ilkka at The Fourth Checkraise.
A few years ago I read "Profiles, Probabilities, and Stereotypes," an excellent book about why us finite beings who have to make important decisions under limited information not just necessarily need categories, generalizations and stereotypes as thinking tools, but why it is moral for them to employ them. (Even the real victims of stereotyping and prejudice usually simply can't help but themselves stereotype others in a crudely prejudicial manner!) I picked up "In Praise of Prejudice;" by Theodore Dalrymple, an even better book about this topic, and already devoured it during the ride home. The very first sentence, "These days, there is a strong prejudice against prejudice" sarcastically cuts into the heart of the matter, and it just keeps getting better after that.
Stereotypes turn out to be mostly true—a major example of what I once called the primary message of conservatism:"Life is not like that." See also this 2001 article by John Derbyshire, Stereotypes Aren't So Bad.