Mr. Backman didn’t fit into any obvious genre mold, and there was no guarantee that his whimsical, oddball sense of humor would appeal to Americans. Atria was cautious at first and printed 6,600 hardcover copies, a decent run for a debut novel in translation.

The novel got a boost from independent booksellers, who placed big orders and pressed it on customers. The Book Bin in Northbrook, Ill., has sold around 1,000 copies, largely based on word-of-mouth recommendations.

“I passed it around to the rest of the staff and said, I think this is absolutely wonderful, am I crazy?” said Nancy Usiak, a bookseller at the shop. “There are 10 of us, and this was one of the rare occasions where we all agreed.”

The novel’s protagonist, Ove, is a lonely curmudgeon who screams at his neighbors for parking in the wrong place and punches a hospital clown whose magic tricks annoy him. Six months after his wife’s death, he’s planning to commit suicide and has turned off his radiators, canceled his newspaper subscription and anchored a hook into the ceiling to hang himself. But he keeps getting interrupted by his clueless, prying neighbors. He strikes up a friendship with an Iranian immigrant and her two young daughters, who find Ove’s grumpiness endearing.

Once it became clear that there was an appetite for Mr. Backman’s quirky misanthrope, Atria asked Mr. Backman if he was working on any other novels. As it turned out, he’d already written several more.

“I write pretty fast, because I’m high strung,” Mr. Backman said.

Atria bought them all. Last year, it published his novel “My Grandmother Asked Me to Tell You She’s Sorry,” about a girl named Elsa whose grandmother dies, leaving her with a batch of letters to deliver to people her grandmother had wronged in life. The book now has nearly 500,000 copies in print and has spent 26 weeks on the paperback best-seller list. In May, Atria released a translation of his novel, “Britt-Marie Was Here,” about a passive-aggressive woman who leaves her cheating husband and ends up coaching a children’s soccer team in a backwater town.

Last month, Atria bought four more books from him, including the novella “And Every Morning the Way Home Gets Longer and Longer,” a surreal story about an elderly man with dementia who adores his grandson, which is to come out on Tuesday.