When MARY SALSBERG starts her twenty-five-year affair with THOMAS, she is a middle-aged, lonely, separated, overworked mother of two. He electrifies her senses and respects her professional ambitions. So begins a lifelong tangle of emotions.

AN ILLICIT LOVE is unique  among affair memoirs because of Salsberg’s triple perspective. Her affair ends in marriage, making her the other woman, then the wife. She is also a licensed clinical social worker who counsels patients on infidelity issues. This trifecta of experience enables her to analyze her own life.

The story covers the exhilaration of the affair—the Friday night trysts, parties, vacations. But there’s despair, too. The relationship survives breakups, her suicide threat, his wife finding out, and three-way therapy sessions. It even perseveres despite an ironic reality: Salsberg is still mostly alone and lonely in the affair.

Her masochistic emotional roller coaster ride never stops. Not when Thomas’s wife dies suddenly of cardiac arrest. Not in the agonizing time afterward when the relationship hits the rocks. Not even after she marries Thomas.Even today she feels like the second woman in his life.

Salsberg’s story represents a shifting American marital landscape: The number of women having affairs rose almost 40 percent from 1990 to 2010. In roughly the same time frame, infidelity rose 20 percent among wives under thirty and 45 percent among husbands of the same age.

Unlike many books, Salsberg writes about how her relationship played out over many decades. This full, long view enables her to call back to other struggling generations.

While she shares explicit details about the couple’s wonderful sex life, she also pushes readers into deep psychological territory. But Salsberg never succumbs to blaming one person. Instead she explores all the causes and effects of her affair, even those inside herself. For this reason AN ILLICIT LOVE will facilitate the emotional journeys of others who grapple with infidelity.

It will also contribute to the growing cultural conversation about monogamy, love, and happiness.