Sexual Fluidity: Understanding Women's Love and Desire, by: Lisa Diamond (2008). An excellent book on female sexuality and how women are more likely to fall in love with people than with a specific gender.
The G Spot: And Other Discoveries about Human Sexuality, by: Khan Ladas, A.K., Whipple, B., & Perry, J.D. (2004). An easy read that offers information on how to access the G Spot and provides other excellent sensual recommendations.
Becoming Orgasmic: A Sexual and Personal Growth Program for Women, by Heiman, J., & LoPiccolo, J. (1987). An oldie but a goodie, this book is wonderful guide designed for women who are have encountered obstacles that are keeping them from achieving sexual satisfaction.
Coping With Erectile Dysfunction: How to Regain Confidence and Enjoy Great Sex, by Metz, M. & McCarthy, B. (2006). A great read for the man who is suffering from erectile dysfunction.
Coping With Premature Ejaculation: How to Overcome PE, Please Your Partner & Have Great Sex, by Metz, M. & McCarthy, B. (2004). Provides information on Premature ejaculation from a multidimensional, bio-psychological approach and offers recommendations for how to cope with this problem and strengthen your sexual relationship. An excellent resource for couples.
When Sex Isn't Good: Stories & Solutions of Women With Sexual Dysfunction, by Goldstein, S.W. (2007). Provides information on a variety of women's sexual health issues with a focus on empowering women to discuss their sexual dysfunction with their partner and healthcare provider.
The Man Who would be Queen: The science of gender-bending and transexualism, by Bailey, M. (2003). An excellent book on transexualism, the author does a remarkable job incorporating real-life stories with scientific fact.