Dani Shapiro was used to hearing it: “There’s no way you’re Jewish.” With her blond hair, blue eyes and delicate features, Shapiro has long been easy prey for cultural assumptions.

Shapiro must be your married name, she’d heard more than once. A family friend (Jared Kushner’s grandmother, as it turns out) took things a step further: “We could have used you in the ghetto, little blondie. You could have gotten us bread from the Nazis.” Never mind that the 56-year-old author was raised as an Orthodox Jew and studied the Talmud; she has, as a blogger put it, “a look that would qualify her for the role of lead shiksa in a Woody Allen movie.”

Now, in her new book, “Inheritance,” Shapiro reveals the shocking result of an over-the-counter DNA test: Biologically speaking, she is very much qualified to play lead shiksa. In fact, her memoir — a modern-day mystery with a neurotic heart — could easily be the screenplay for a Woody Allen movie.

The tale begins innocently, in a casual moment at Shapiro’s Connecticut home. Shapiro’s husband, curious about his own roots, has sent for one of those genetic kits that promises to tell “a more complete story of you.” The vials lie around the house for a while, become “part of the scenery,” resting ominously on a kitchen counter as the couple goes about its daily life. One night, Shapiro’s husband unwraps the containers and nonchalantly tells his wife to spit in one. Without much thought, she does. “I felt vaguely ridiculous and undignified,” she writes. “Why was I even doing this?”

Shapiro, a self-professed “serial memoirist,” had, after pages and pages of introspection, become quite certain of who she was. Over the course of a decade — and four memoirs — she documented a personal life full of dramatic twists. In “Devotion” and “Slow Motion” Shapiro divulged the tumult of her early adult years — her relationship with the stepfather of a close college friend, the car accident that killed her father and nearly destroyed her mother, the rare illness that threatened her young son’s life. In “Still Writing” and “Hourglass,” Shapiro shared the experience of working her way through her troubles and building a mostly happy family life after two failed marriages.

“I am no longer consumed by the question: What if?” she wrote fatefully in “Hourglass.”

“Inheritance” is consumed by the question of what if. What if the man Shapiro thought was her father is not? What if she could find the man who is her biological father? What if he doesn’t want anything to do with her? What if he does? What if she is not who she thought she was?

The first unknowns slip away easily: Shapiro’s DNA test, compared with that of her half sister, indicates the father who raised her was not her biological father. Identifying the man who is turns out to be almost as simple and quick, thanks to the internet.

But solving the other mysteries proves more difficult. Shapiro wrestles with questions both mundane and profound: how to get in touch with her biological father without scaring him away, how to share the news with her teenage son, how to look at old family photographs and understand her connection to the people in them, how to reconstruct, as she puts it, “the narrative edifice” of her life.

“Inheritance” is fundamentally a tale of soul-searching. Much of the book consists of Shapiro processing each new bit of information. She seeks guidance from friends, rabbis, ministers, Buddhist monks, even an acupuncturist. At times, her literal and philosophical quest is overly self-involved and melodramatic: “I am the black box, discovered years — many years — after the crash. The pilots, the crew, the passengers have long been committed to the sea. Nothing is left of them. Fathoms deep, I have spent my life transmitting the faintest signal. Over here! Over here!” Just because the black box has been recovered doesn’t mean everyone wants to know its contents.

Still, as at-home genetic tests become more popular and stories like Shapiro’s become more common, “Inheritance” offers a thought-provoking look at the shifting landscape of identity.