SHARK HEART: A Love Story, by Emily Habeck

In Emily Habeck’s beguiling first novel, Lewis and Wren have been married for only a few weeks when Lewis is diagnosed with a Carcharodon carcharias mutation. That explains his nose turning to nothing but cartilage, his intense thirst and appetite, and all those loose molars. By the end of the year, Lewis will transform into a great white shark. When he tells Wren the bad news, she quips, “They say the first year of marriage is the hardest.” The joke has a hard kernel of grief at its center — because, of course, “there would not be another year to measure against this first one.”

This isn’t only a whimsical concept, though it’s that too. “Shark Heart” succeeds because it doesn’t function solely on the level of metaphor. In the world of the book, human-to-animal mutations are a lamentable but very real fate, like metastatic cancer or mental illness. The process is described with such specificity and physicality that the fantastical becomes, if not mundane, then at least believable. An acquaintance at the gym swimming pool is pregnant with peregrine falcons; another woman’s brother is becoming a zebra. Wren herself is no stranger to the brutality and loss of such mutations; they’re a defining fact of her upbringing, though Habeck withholds this past from the reader for as long as possible.

Over the course of six months, Lewis’s limbs turn to fins in an agonizing process of bone agglutination. His eyes stop closing. To Wren, who buys a fish counter’s entire inventory to keep up with Lewis’s appetite, they come to resemble “a black marble resting atop each temple.” By the time she drives from their home in Texas to let her lover swim into the Pacific, the loss feels as vivid and painful as any marital tragedy. Habeck’s setup allows her to grapple with big questions: What is the self, anyway? And how do we process enormous loss? When I read this line, I sighed in recognition: “The main ingredient in transformation was not magic. It was pain.”

“Shark Heart” is much shaggier than its easy-to-imagine elevator pitch: Husband becomes a shark and breaks his wife’s heart. The story is told neither chronologically nor in a straightforward manner. The beginning zigzags from the couple’s newlywed days to their early courtship to Wren’s childhood to her college years and back again. Traditional scenes are interspersed with fragments of conversation written as play dialogue and stage directions; it’s all fittingly chimerical. Many of the novel’s 400-plus pages contain only a sentence or two, an approach that imbues the smallest interactions and moments with poetic weight.

The novel is most striking when Lewis knifes through the ocean as a shark. “Exiled from the plane of conversation and things and doing and going and seeking and becoming,” Habeck writes, “Lewis simply existed.” In a world where human behavior is responsible for the extinctions of so many other species, the idea of an animal perspective blotting out human consciousness is at once absurd and deeply startling.

The weakest aspects of “Shark Heart” are Wren and Lewis themselves. For much of the book, they feel as flat as rom-com log lines: Lewis cast as the romantic, a manic pixie dream boy, with Wren as the strait-laced realist, guarding her heart. We’re told that they’re meant to be together, but Habeck doesn’t show their connection — which makes it more difficult to believe the book’s otherworldly premise. The elided trauma of Wren’s youth would better inform her point of view and characterize the marriage better; the withholding felt more like trickery than plot twist. And some of the language strains. Wren at 18 “smelled like the wind,” for instance. (What does wind smell like?) I also struggled with this phrase: “Lewis tattooed her with beautiful poetry in a place she would never see but somehow read every second.”

In the end, I forgive this debut its flaws because it’s surprising and pleasurably uncategorizable. “Shark Heart” is wild, in every sense of the word.

Edan Lepucki is the author of “California” and “Time’s Mouth.”

SHARK HEART: A Love Story | By Emily Habeck | 416 pp. | Marysue Rucci Books | $28