Max -
One of our local heroes out here is Tom Ball. He has written "A Sourcebook of Sonny Terry Licks for Blues Harmonica". Tom's a pretty thorough guy, and his book covers lot's of discussion about Sonny's style, as well as the usual licks that a book like this, as it's title implies, would show. CD is included, and it is available from Elderly. (If you can find the URL for Folk Mote Music Store of Santa Barbara, CA, that is one of his home bases; he occasionally does lessons through those fine people. They would also be happy to sell you one of his books.
Tom Ball has written some other books, too. One is an interesting look at the bawdy blues, with illustrations by R.Crumb.