There’s something inherently appealing about a novel that makes Deborah Solomon, the New York Times Magazine Q&A guru, the crush object of a 15-year-old Canadian boy.

“What do you like so much about Deborah Solomon?” Logan Troutman’s cool, 28-year-old aunt, Hattie, asks him, having spied the plea, “Deborah Solomon, be my girlfriend,” written in the coating of dust on the family TV.

“The older woman thing?” Hattie guesses.

That isn’t it, turns out. “She’s solid,” Logan says after some prodding. “And she doesn’t back away from s—.”

Solidity and spine are sorely lacking in Logan’s life. His mother, Min, is manic-depressive, suicidal, psychotic, and unlikely to get much better anytime soon. His father, Cherkis, is a goodhearted guy but MIA; he left years ago, at Min’s insistence, and has barely been heard from since. When Min gets so sick that Logan and his precocious little sister, Thebes, are left to fend for themselves, Thebes calls Hattie in Paris, where she’s just been dumped by a wishy-washy boyfriend, and asks her to please come back to Manitoba and help.

Hattie, Min’s younger sister and the narrator of the tale, tries briefly to hold things together on the home front, but she has no desire to be a substitute mother to her niece and nephew. So she packs them into Min’s Ford Aerostar and sets off to South Dakota, then across the American Southwest, in search of Cherkis.

So begins the black comedy that is Miriam Toews’s “The Flying Troutmans” (Counterpoint, 274 pages, $24), a road-trip novel about three broken hearts in need of mending. Complete with sullen teenage brother, endearingly odd tween sister, failed suicide attempts, ailing van, and indie quirkiness, the novel bears some resemblance to the movie “Little Miss Sunshine” — though with her disinclination to bathe or brush her teeth, 11-year-old Thebes (real name Theodora) is unlikely to win any beauty pageants.

Thebes is, however, a spectacular child; we’re sure of this as soon as she greets Hattie at the airport. “She had fake tattoos all over her arms and her hair was intense purple, matted and wild, and she melted into me when I put my arms around her and tried to lift her off the ground.” She talks like a small, urban tough (“Wassup, player?”); packs a dictionary, a mannequin head, a hole puncher, assorted art supplies, and zero clothes for the road trip; has a habit of making oversize novelty checks for people she loves, and cc’s David Geffen whenever she writes a song.

Ms. Toews (“A Complicated Kindness”) is masterful at channeling children. The relationship between Logan — forever retreating into his hoodie, headphones blaring — and the irrepressible, incessantly chatting Thebes is volatile in all the normal ways, but extraordinarily tender, too, in the manner of siblings who know they can count only on each other.

The author is less skilled, however, at rendering the relationship between Hattie and Min — at rendering anyone’s relationship with Min, in fact. The reader is told repeatedly that Min, when healthy, is irresistible, that this is why her husband stuck around for as long as he did, that this is why her children are so bereft, that this is why Hattie loves her so. But Ms. Toews fails to show us this; we catch only the most fleeting glimpses of a semihealthy, or at least not unambiguously ill, Min. Even in flashback, Min is the least distinctly drawn of the main characters.

The novel is set roughly in the present, and our alienated trio is adrift in an alien land, at which the novel takes some amusing potshots. But the road trip, entertaining though it is, feels contrived; it’s certainly unlikely that the Troutmans would set off without making at least a cursory attempt to track Cherkis down online first. Also peculiar is the dependence on pay phones, which Hattie, without a cell phone, finds and uses more often than seems likely these days. And how is it that Hattie, whose Paris apartment is stocked with psychology books, still doesn’t understand the chemical nature of Min’s mental illness? How can she still take the romantic view, believing that love — her own love — can save the sister who tried to drown her when they were young?

As the imagery keeps reminding us, the Troutmans are at sea, drowning even as they hurtle through the desert. The novel is a little bit at sea, too, but the buoyancy of Thebes and her big brother keeps it from going under.