It doesn’t take long for the main character in Joshua Ferris’ new book “The Unnamed” (Reagan Arthur Little Brown) to walk out on his beautiful wife. Her devotion is so extraordinary she dresses and packs him for the trip, then later combs the streets until she finds him passed out under a tree and brings him home. You’d think maybe there was some sort of intoxicant involved, but no — Tim Farnsworth isn’t the character who ends up with the drinking problem. Tim’s problem doesn’t have a name.

It just has an action: walking. Spells of a mysterious compulsive state set his feet bulldozing forward, rendering him incapable of stopping even for a hat and gloves and only vaguely able to chart his own course. He walks until he exhausts himself, then collapses into an exquisite sleep until he wakes and calls his wife, Jane, to come find him and bring him home.

By the time we join them, he’s on his second months-long bout with these unpredictable forced marches, and the options are pretty grim all around. They’d tried every intervention from Swiss specialists to 3 psychiatrists to grass-and-carrot smoothies with colonics the first time around, but eventually the only treatment that remained was to handcuff Tim to the bed and keep watch over him until the spells disappeared as suddenly as they’d arrived.

The first crisis had been long but acute, we’re told. When it ended, the Farnsworths returned their attention to their daughter, their careers and trying to savor each blessed day of not-sick while also basking in the appreciation of dullness that only comes after a long stretch of living a life that’s un-dull in a very unpleasant way. But the illness’ recurrence changes the name of even that calm period from “right after the cure” to “those couple of years in remission,” and they both know now that their marriage is going to be one of the ones forced to confront its vows about sickness and health head-on.

And that’s hard enough when your condition has an actual diagnosis.

Actually, what surprised me about Tim’s walking psychosis was how joltingly familiar Ferris’ description of it felt. I was suddenly rushed back to the 2 clearest nadirs of my life, pushing back against a steady diet of upheaval by narrowing my focus to only the 2 extremities on the bottom of my body and putting them, one and then the other, in contact with the pavement. I couldn’t have told you in either case why I did it — I just found myself putting on my shoes and going out the door, winding up and down streets until my breathing changed and my shoulders released a notch and the static-y cloud of emotions blurred my vision a little less — but I was quite sure of how desperately I needed it. Still, it felt like a small thing at the time, to be summed up with a quick “My therapist says I should get more exercise,” and so to see that compulsion and release blown up to many times its size in Ferris’ lyrical urgency was disconcerting.

“I think that walking is one way of sort of reconnecting with your body, with the world, with other people, with the streets of your city or the beautiful landscape of your countryside — whatever it may be, walking brings the world to you,” Ferris said by phone from his home, where he notes that living in Brooklyn, New York has accustomed him to plenty of foot-based travel. “So it’s very nurturing to me; it’s something I enjoy doing. Walking has a long literary history as well: Wordsworth was a good walker, and it was incorporated into romantic poetry in particular. So in some way I started thinking about the way in which walking is related to the intellectual life. I was playing with my ideas about how rejuvenating a walk can be, but also the literary aspect of it.”

Funny that Ferris should call it rejuvenating, since it just about destroys Tim. “It’s really the opposite for him, and that was the idea. When walking becomes a disease, all the ways in which walking is rejuvenating for the average person become unendurable. It’s the flip side. You know, most people walk for health reasons, so this was just to see what might be generated by it” if continued unchecked. Score another one for the old “moderation in all things” adage.

His 20-year marriage to Jane, of course, means that his everything generated by his illness happens to two people, not just one. The tides of their partnership change over the years spanned between the book’s covers, and Ferris does a beautiful job of letting the characters swirl in the eddies while remaining rooted to who they truly are. One passage haunted me for days by summing up in a few deft sentences the motley threads which make up the ties that bind:

“The long matrimonial haul was accomplished in cycles. One cycle of bad breath, one cycle of renewed desire, a third cycle of breakdown and small avoidances, still another of plays and dinners that spurred a conversation between them late at night that reminded her of their like minds and the pleasure they took in each other’s talk. And then back to hating him for not taking out the garbage on Wednesday. That was the struggle.”

It’s the sort of intimate, studied portrait that made me wonder if Ferris shares my half-gawking, half-intellectually-curious fascination with what makes any marriage tick. “Who isn’t interested in that?” he answered. “What makes 2 people who come together, stay together? The human being himself (is complicated), and then two of them get together and become a unit — it’s just that much more complicated. So I take great delight in trying to figure out what makes a couple work. But I’ve come to the conclusion after watching my friends divorce that there’s something in the way of (my) understanding (it). A full understanding would require you to be really in bed with them, and not just literally — you’d have to be inside their partnership when somebody is giving, cruel, funny, loving. All of these things happen without anybody else knowing about it, so their secrets are truly between 2 people.”

Incomplete understanding is hardly ever a barrier to passing judgment, however. And to tell you the truth, I really hated the way Jane got treated. It wasn’t so much by Tim, although a couple of his carelessly self-centered ways made me want to reach onto the page and bop him, or even really by Ferris, whose honest sympathy for her doesn’t waver as he walks her through a colossal mistake or two. What stuck in my craw was probably the bare reality of the situation: All of the big things that happened to Tim also happened to her — the physical decay, the loss of career and a normal family life — and while some of them were vicissitudes that happen in any life, many were a direct result of being yoked to him. They unfold in a causal way that’s not really susceptible to blame, yet it’s hard to escape the feeling that she’s Ginger Rogers, doing everything Fred Astaire did only backwards and in high heels.

“She gets the short end of the stick,” agreed Ferris. But he’s not sure that her character, in either the fictional sense or the archetypal one, would have been happier with any of the other choices available to her. She loved Tim Farnsworth enough to marry him, to sleep next to him for twenty years, to share thousands of meals, to create and raise a new life together, to chat over a newspaper every morning and embark on a routine of illicit delights in a public restroom. These things weren’t a service to Tim; they were the construction of the life she wanted. Her devotion to the marriage is less a fulfillment of her promise to him than it is a measure of herself, so when she takes that private internal stock that we all do, “she sets her level back to her love of this man. And she fails on occasion, but where she succeeds, hopefully she herself might view herself in a sympathetic way as a wife. Because everyone knows that to go backwards in heels is much harder, and the neglect of that remarkable feat makes it even more difficult. So you know, I think about her as a real person. One would hope that she herself could say she’s a quiet struggler who’s trying her best to hold it together. And she has respect for the way that she feels, but it was of course made out of love.”

Leah DuMouchel is a free-lance writer who covers books for AnnArbor.com.

Joshua Ferris reads from "The Unnamed" in the Helmut Stern Auditorium of the University of Michigan Museum of Art at 5:15 p.m. on Monday, January 25. Admission is free.