One of the more accessible stage dialect books, and very popular. It breaks down each dialogue well, and uses the International Phonetic Alphabet as its standard for presentation (and teaches it along with the dialects). The tape set that's meant to go with it is very hard to find, and overly expensive. Most people who are serious about the subject, however, will want to try to find them.
From what I've been told, this is actually one of the "bad" dialect books. BUT - it actually came in very handy for me several times. Again, a good book for artists to have on hand.