Esther Perel. The secret to desire in a long-term relationship TedTalk
See other Perel TedTalks or read her book, Mating in captivity. (available at the GVPL)
The Erotic Mind, Unlocking the Inner Sources of Sexual Passion and Fulfillment Jack Morin. (book)
Sexual Intelligence, Kim Catrall. (DVD available at the GVPL)