In the latest novel by accomplished author Jean Hanff Korelitz (Admission, A Jury of Her Peers), which shares the title of its main character’s book, relationship challenges raise questions of how often we really know what’s best, whether living the life we’ve envisioned necessarily means we’re living it right, and how we overlook our instinctive responses to the people we meet.

Grace Reinhart Sachs’ cynicism toward the wedding industry understandably follows from her work as a couples’ therapist. If there were more emphasis on marriage and less on the wedding, she postulates, 50 percent of couples wouldn’t get married at all—likely the ones who shouldn’t have been together to begin with.

That philosophy is reflected in her self-help book, You Should Have Known, in which she argues that many women would have long ago ended their relationships, had they only followed their instincts. Grace is juggling her private practice and her son’s New York City private school demands while amping up for the book’s release. The fielding press inquiries from Vogue, Cosmopolitan, “The Today Show” and “The View.”

Then her life takes an unthinkable turn: Her own picture-perfect marriage is called into question. Although she cautions her patients and readers against love at first sight, that was her experience with her pediatric oncologist husband, whom she met during her senior year of college. Grace goes into a tailspin, questioning the man she’s known for more than a dozen years, as well as the relationship that defines all her interactions and her very worth as a counselor.

You Should Have Known is an insightful, compelling tale sure to provoke reflection.

“Cryptography involves one genius trying to work out what another genius has done—it results in the most appalling carnage,” observes one Decoded character. In this debut novel from Mai Jia, eccentric math prodigy Rong Jinzhen is plucked from his studies at N University and recruited to China’s top-secret Unit 701. There he’s tasked with deciphering PURPLE, a fiendishly difficult code used by China’s enemies. In doing so, he’s involved in an intellectual race against a shadowy opponent who’s bent on deciphering PURPLE before he does. His rival turns out to be his trusted former university mentor—or so it seems.

Despite a plot based on high-stakes political intrigue, Decoded is hardly a straightforward thriller. Instead, it begins as a family saga, narrating the lives of such figures as Jinzhen’s grandmother, a pioneering mathematics professor. Events are told out of order, through a combination of narration and after-the-fact interviews with key characters. The reader must wait to the end to find out who is telling this story, and why. And the tale builds to a final crisis that reveals the fragile nature of genius.

Along the way, it offers a fascinating window into 20th-century Chinese history, including World War II and Mao’s Cultural Revolution (one character is subjected to public humiliation as a supposed traitor to the Party). And it sheds light on a mysterious profession, one that conceals sense within nonsense, “as if a sane person had borrowed the words of a madman to speak.” Evocative metaphors convey the seductiveness of Jinzhen’s calling to even the math-averse. While some of the novel’s factual questions are ultimately answered, its psychological portrait of a brilliant man suggests that the human mind is the deepest enigma of all.

If you’re very observant and know a little something about the wilder shores of human genetics, then you may be able to figure out the big mystery of Carol Cassella’s new novel by, oh, page 260 or so. Oh yes, the title also gives one a hint as to what’s going on with one of the book’s well-drawn characters. But we should start at the beginning.

Gemini concerns a dedicated and humane doctor, Charlotte Reese, who comes to be the physician for an anonymous woman who is medevaced in from an impoverished Washington town to Dr. Reese’s Seattle hospital in the middle of the night. The Jane Doe is apparently a hit-and-run victim. Conscious when she was first found lying in a ditch by a road, she slips into a coma on the operating table after a fat embolism breaks loose from one of her broken bones and lodges in her brain. Part of the story concerns Charlotte’s struggle over whether to keep Jane Doe alive, or to let her pass on with some kind of dignity.

The other part of the story has to do with Charlotte’s boyfriend of three years, a writer who’s working on a book about genetics. He’s one of the folks in this book whose DNA doesn’t work the way it should. Having inherited neurofibromatosis, as a child he was subject to seizures and later developed benign brain tumors—yes, more than one. Charlotte, who’s desperate to have a child, doesn’t know if Eric’s a good prospect for fatherhood, as the risk of him passing down his affliction is almost a certainty.

But there’s still the problem of Jane Doe. Surely, with the whole world interconnected, she must have family; she must have someone who misses her. Cleverly but incrementally, Cassella—a practicing physician as well as an author—puts together the pieces of Jane Doe’s mystery even as she ponders, through Charlotte, the Big Questions. What is life, anyway? Is it simply one’s genetics? Does it have a purpose? What’s the best way to find love, happiness, peace? Is Jane Doe still in there somewhere, in her ruined, swollen, already decaying body?

As for the mystery’s solution: It explains much, but that’s all you’ll learn from this review!

Gritty downtown Boston and the awe-inspiring but unforgiving North Atlantic coast come to life in Elisabeth Elo’s debut suspense novel, North of Boston. Elo shows us the Eastern seaboard through the fiercely loyal, ceaselessly skeptical and fundamentally fearless eyes of Pirio Kasparov. When the lobster boat Pirio is working on is struck and sunk in Boston Harbor, killing her friend Ned and nearly killing Pirio, she doesn’t believe it was an accident. For her own sake, and for Ned’s 10-year-old son Noah, Pirio starts asking questions and doesn’t stop until she has looked everywhere for answers.

Elo maintains suspense throughout by making it unclear whom Pirio should trust with her inquiries. Can she depend on her moody Russian father, Milosa, head of a perfume empire? Old flame John Oster? The mysterious journalist who turns up at Ned’s funeral? Her best friend, Thomasina, Noah’s mother and a struggling alcoholic? Elo creates likable but flawed characters all around, which keeps us guessing right along with Pirio.

It’s hard to say which is the bigger star of the novel: Pirio or the places she goes. Elo evokes city bars, harbor politics and ocean voyages with equal ease. As much as Pirio belongs to the streets of her city, she’s also magnetically drawn to the sea. When Pirio boards a ship headed for the Canadian Arctic, we see the rocky coast and feel the sea spray right along with her. The later scenes in the whaling grounds of Cumberland Sound will both shock and inspire readers with their blend of realism and majesty.

While the tangled story behind Ned’s murder leads Pirio down so many paths that the ultimate connections between them all can feel a bit forced, readers will nonetheless be rooting for the doggedly determined Pirio right to the end.

When you are a rational human being, with free will and agency, is there any such thing as a point of no return? That’s the question Yvonne Carmichael finds herself asking after she’s charged with murder in this dark, intense, wholly engrossing British import, Apple Tree Yard.

A well-known London scientist, Yvonne has spent her life on the straight-and-narrow: successful career, two grown children, happy if ho-hum marriage. (“The reason he ambles into the kitchen and asks for his car keys is not that he is incapable of locating them himself; it is to remind me that after many years of marriage, he still loves me,” she muses during their morning routine.)

Then Yvonne meets a mysterious man while walking back to her office after a routine meeting, and begins an affair. She starts making dicey choices, including a public tryst in an alleyway called Apple Tree Yard with thousands of commuters walking by just a few feet away.

Later that night, Yvonne is the victim of a savage sexual assault, and soon suspects her attacker is stalking her. Going to the authorities would risk uncovering her affair, so she enlists her lover to help scare off the attacker. But things go horribly wrong, and suddenly this woman who has played by the rules all her life finds herself judged by a wholly different standard.

Novelist and journalist Louise Doughty is a masterful writer, improbably making Yvonne a sympathetic, insightful character even as she is cheating, lying and generally making the worst possible life choices. Doughty also perfectly captures the quiet details of domestic life, the erotic charge of a high-stakes affair, the crackling drama of a courtroom. She dispatches the notion that we are masters of our own fate, chillingly illustrating how quickly we can derail our own lives.