The G-Spot, by Cathy Winks; the good vibrations guide.

from the back cover:

"The G-spot has long been regarded as one of a woman's most mysterious elusive and sought-after pleasure zones - but now, expertise is within your reach.  The Good Vibrations Guide:  The G-spot explains:  how to find the spot, how to let your partner in on the secret, how to enhance your G-spot has fared through medical and literary history.  You'll also find an eye-opening anatomy lesson and no-nonsense debunking of the myths surrounding female ejaculation, with references and a bibliography.  Whether you're just starting out or a practiced G-spot explorer, the tips and techniques in these pages are3 sure to hit the spot!"

Down There Press, 2007