Penny Guisinger’s delightful “Shift: A Memoir of Identity and Other Illusions” returns more than once to the image of a Mobius strip. A one-sided surface in the shape of an infinite loop, the Mobius strip is both simple and profound (it’s worth a quick internet search to learn how to make one by twisting a strip of paper). In “Shift,” it serves as a symbol of a life, traversing terrain that is at once mysterious, mundane and transformative.

In its broadest outlines, Guisinger’s memoir is focused on one specific shift: in her late 30s she falls in love with her friend, Kara, and leaves behind her husband and straight identity. Guisinger’s short chapters unfold swiftly, in vivid bursts of detail and association. Reading them evokes the experience of meeting a new friend for coffee and hearing intriguing nuggets about her life and preoccupations: episodic, but not linear; quick, but not superficial.

Her voice is searching, forthright and witty: “Shift: A Memoir of Identity and Other Illusions,” by Penny Guisinger. University of Nebraska Press, $22.95 “Imagine that you are a thirty-eight-year-old woman and the primary breadwinner in your house.

You are the mom of two kids, ages three and one. ..

. Your marriage is a rickety house built on spindly stilts straddling a fault line in an earthquake hazard zone, so sometimes you think you might be working for FEMA, but you’re not issued a hardhat..

. You are sure you ordered the everything bagel of feminism topped.