Before I can tell you about The Unnamed, by Joshua Ferris, I have to tell you about my daughter. Not all about her. Not even a lot about her. Just one episode, in fact. One day, when she was about 15, I picked Sarah and her friend, Arianne, up after school. "Dad, what is up. I mean, what is up." Arianne chimed in, "Yeah, what...is....up." And so on for the next 20 minutes or so. Neither of these teenagers was ever close to valley-girldom, so I attributed their fascination with this one phrase to a mild, peer-borne infection of something or other and hoped it was brief. It was, and it was. I'm mentioning it now because I want to convey how striking it was to hear a normal question, what's up, transmuted into an entirely different sort of element simply by undoing the apostrophization and exercising the option of changing it from a question into a statement. Keep that transmutation in mind when you read the next paragraph.
So, the bottom line on The Unnamed is that it's great, if you 1) buy the premise, and 2) accept the characters' response to dealing with said premise. The premise is a sudden occurrence of a disease/condition that requires Tim to walk, regardless of circumstances. There's no precedent to be found in the medical/psychological literature. I could buy that. How the family members - Tim, his wife and daughter - choose to cope with it will strike some as implausible. I don't know if it'll ruin the book, though, because there are some arresting issues addressed, mind vs. body and the nature of love and spousal duty being the most significant. I had some difficulty with #2, but loved the book anyway. You have to care about the characters, and the writing's superb throughout. Especially at the very end. Not to spoil it, but nothing happens. (Reread paragraph one if necessary.)
I'd bet that most people who've also read Ferris's first novel, the darkly comic Then We Came to the End, will prefer that one. As much as I enjoyed it, my vote goes to his new book.
FYI - I'm presently in "'sup" mode. As in, "Dude, 'sup?" "Yo, 'sup." Does away with meaning altogether, reducing the utterance to mere acknowledgment of another's presence. Punctuate it any way you want, depending on how much you're interested in having a conversation. And there's no danger of having one's teenage daughter and her friend go apeshit saying, "Is up." to each other for the better part of an hour. At least there better not be. Hmm, when Tim was first struck by his walking compulsion, his daughter was about Sarah's age when the "What is up" episode occurred. Could it be that his daughter came home from school one day and besieged her father with an extended riff on that phrase? Why didn't Ferris reassure me that that's not what happened? What's up with that? I mean, what is up with that. Wait, I guess it's "what is up with THAT?".