As the author ticks off a chapter for each character, there is the dread that “Nine Perfect Strangers” will unfold methodically and not all that excitingly. The daily meditation, diet and exercise routines are chronicled down to each mandatory smoothie. The proprietress’s grandiose ideas about what she will do for her guests take up significant space, too. People duck each other at first, then begin talking way too much about the problems that brought them to Tranquillum — and there is no limit to the number of subplots Moriarty is eager to cram into a single book. Some of the problems are tragic (lost children; yes, that’s plural). Others (an addiction to cosmetic surgery, the miseries of winning the lottery) are silly beyond belief.

Image Liane Moriarty Credit... Rachel Kara Ashton for The New York Times

But there’s more going on here than just confessional chatter. Moriarty has tapped into a trendy therapeutic topic that gives her book its novelty. It should stimulate her fan base’s curiosity, and it gives this otherwise bland book an excuse to go way off the deep end. And it brings out the most extreme behavior in everyone present, especially Masha, the proprietress, who was none too stable to begin with. Not even the Buddha gets out of “Nine Perfect Strangers” without sounding slightly menacing once the book hits its temporary insanity phase. (“Ardently do today what must be done. Who knows? Tomorrow death comes.”)

At least Moriarty quickly abandons her slow rollout of characters and days and lets the scene at Tranquillum begin to jell on its own. Frances is by far the best of the bunch, even if at 52 she thinks about menopausal hot flashes a lot. Her career writing bodice-rippers began with something called “Nathaniel’s Kiss,” its hero “a heady mix of Mr. Rochester and Rob Lowe.” Somehow, she got away with that for a long time. But two husbands and a lot of books later, she’s washed up and at an impasse. Still, she has a writer’s gift for bestowing colorful nicknames on all this story’s other characters and deeming herself the central figure.

“It’s all about me,” she says at one very odd moment. “I’m just not sure of my love interest yet.”

Rest assured that there are candidates for that honor. Moriarty didn’t put this book together to send everyone home as unfulfilled and wretched as they started. Each person reveals why he or she is so enraged, vain, sulky, frustrated, disappointed and so on. And if all it took were the Titanic staircase and a few stiff hikes to turn lives around, what an inspiring story this would be. Unfortunately, Moriarty is so wildly out of control that the same book that emphasizes wellness also includes one character’s healthy smack at another with an antique candelabra.

After the huge success of “Big Little Lies,” Moriarty has become a Hollywood darling despite the uneven caliber of her earlier work, and Nicole Kidman is already involved in a film version of “Nine Perfect Strangers.” She fits the physical description of the exotically beautiful 6-foot Masha, but it will be interesting to see if she wants to play anyone quite so … challenging. In any case, this book won’t lend itself as easily to screen adaptation, since such odd things happen to such fundamentally uninteresting people. Moriarty’s books are usually more firmly anchored in the tangible world.