He's Just Not Up for It Anymore by Susan Yager-Berkowitz

An estimated twenty million American men and women are in relationships in which the man has stopped being sexually intimate. Is the problem physical, emotional, or psychological—or are these guys simply bored with their partners?

To find answers, bestselling author and relationship expert Dr. Bob Berkowitz and his wife, Susan Yager-Berkowitz, began an unprecedented survey of more than four thousand men and women in this situation, gathering data and following up with hundreds of interviews with selected respondents. Why Men Stop Having Sex provides a unique window into the sexless man's mind—so that men and women can understand this important issue and begin to address the problems that have inhibited intimacy, and ultimately solve them.