Seeing Voices: A Journey Into the World of the Deaf
by Oliver Sacks (c) 1989

Oliver Sacks has never written a dull book and this one is even better than most. It is not only a history of deafness, it is at the same time an ethnobiography of Deaf* culture, a primer on childhood development and language acquisition, a philosophical inquiry into what makes a language, and (as in all of Sack's books) a series of fascinating case studies.
* Something I learned from the book: Deaf with a capital "D" refers to a cultural group. "deaf" refers to a medical condition.