After more than a decade of "marriage" to a woman with whom she was raising a daughter, Jan Clausen fell in love with a man, stunning herself and the lesbian community to which she had been intimately connected.

The experience was, she writes, "like deliberately embarking on a sea cruise off the edge of a flat Earth." In her luminous and affecting memoir, Clausen charts the trajectory of her sexual life - from her first kiss to her later loves - and offers a stinging critique of society's insistence on yoking identity to desire.

In the 1950s Pacific Northwest, Clausen grew up in a family in which premarital sex, swearing, and spicy foods were verboten. In the sixties, she embraced the heterosexual revolution, consorting with various adolescent Lotharios and failing miserably in her effort to become a topless dancer during a summer break from Reed College. But it was amid New York's dynamic lesbian milieu in the 1970s that she "crossed the pass of love" and fell for Leslie Kaplow, also a writer and activist.

As a couple, they immersed themselves in the city's feminist literary scene and eventually launched their own magazine. In time, however, Clausen grew restless in her personal relationship and uneasy with what she calls People in Groups, those enforcers of ideological purity. She discovered sweet escape in Nicaragua, whose war-ravaged streets would provide the backdrop for her unpardonable act: falling in love with a West Indian male lawyer.

Apples and Oranges is a testament to the powers and perils of desire. It is also the story of one woman's mourning for the community that cast her out and a dazzling examination of the ways in which we all search for identity. Rejecting all efforts at sexual sorting, including the label "bisexual," for her own journey, Clausen arrives at an understanding whereby both likeness and difference emerge as deeply erotic.