I like the books by Martin Seligman. There are lots of books out there, by many authors....each with their own slightly different angle, and some are work/ exercise books.
My experience though was that it was good to read material whilst at the same time seeing a therapist who could help me practice what I was learning through my reading.
Saffie me 46 H 46 M in 1986 D20,D18,S16,D13 H's A 01/05 to 07/06 H recommitted to M 07/06 renewed vows 09/06 Going from strength to strength