I'm not sure that Joshua Ferris's new novel The Unnamed, good though it is – at times, very good – is the novel someone should pick up during these days of sub-zero temperatures and cloudy misery. That goes doubly so for fans of Ferris's excellent first novel from 2007.

The sublimely comic and caustic Then We Came to the End. Ferris's The Unnamed is a bleak if fascinating read, more reminiscent in mood and tone of Cormac McCarthy's The Road than Ferris's National Book Award-nominated debut. If your life is going along swimmingly and you love winter, then this book's for you.

If not, be warned.The "unnamed" of the title is a very strange malady afflicting Tim Farnsworth and, by extension, his wife, Jane, and daughter, Becka. At any moment, whatever he is doing at the time, Tim will get up and begin walking.

He can't stop himself. He will walk and walk for kilometres and kilometres until he is overcome by exhaustion, collapses and goes to sleep, resembling more a homeless person than the wealthy law partner he is.Back at the spacious family home, Jane will await his phone call to come and fetch him.

Sometimes she won't wait and, finding him gone from their bed, will go out hunting for him. So frequent are these incidents that Tim doesn't go anywhere without a backpack containing food, warm clothing and a GPS to help him survive. He's not always successful in holding off the cold, and loses several toes and fingers to frostbite. Ferris paces this novel extremely well – though some of the descriptions of Tim's journey in the second half do get slightly tedious – and doesn't waste any time in getting to the issue. By the fourth page, we are hauntingly told, "It's back." The return of the bizarre malady couldn't have come at a worse time, with Tim being the lead counsel on a very important murder case. (The murder case fits rather oddly in the context of what the book is about, and feels more like it belongs in a Scott Turow novel, not necessarily a bad thing.) But he refuses to relinquish his position, using the excuse that Jane has cancer to explain his sudden and frequent absences. Eventually the truth comes out, and he is stripped of his partnership.That is just the beginning. Slowly, Ferris strips Tim of everything he has come to know: his life, his possessions, his sanity, even himself. In the last third of the book, Tim is virtually unrecognizable when the walking compulsion has completely taken over. The toll this takes on Jane is predictably substantial, even before Tim leaves for good. She ponders an affair, knowing that anything, anything, must be better than what she is going through. How many wives have to handcuff their husbands to the bed just to keep them there?"She hated herself for imagining the concept of a medical prenuptial. You are free to go if he turns too human too quickly. If his body derails, save yourself the grief and heartache of being nursemaid and watchman. Take intact your health and your future and go. You have a life to live. Unburden yourself."Some of the scenes in which Tim is hallucinating are brilliantly rendered, as when he is back in his law office working steadily away. In reality, he is in a coffee shop and his secretary is a waitress whom he pays $100 to give him "an hour to work in peace, no interruptions, no inquiries. Surf the Internet, take a long lunch, talk to your kid on the phone. Whatever – for one hour."No doctor has ever been able to diagnose Tim's demon. Jane and Tim have lost faith in the medical profession. At one point, before the illness has taken over completely, Tim shaves his head and dons a sensor-filled helmet, which he is to wear 24 hours a day. He even wears it to court, where the judge promptly throws him out. It is the only comic element the book has to offer and in the end, nothing comes of the experiment. The walks continue.  To his credit, Ferris never sentimentalizes the disorder, never gets treacly with it. He's not interested in a feel-good story. He knows that the sheer terror of not being able to control what your body is doing and knowing that it is going to ruin the life you have come to love, as well as the people in it who love you deeply, is scarier than anything Stephen King has ever come up with.The fact that this psychologically unsettling novel came out of the same brain that wrote Then We Came to the End confirms Ferris as a brilliant breath of fresh air and a novelist well worth watching.