The first half of the novel has a noir-like feel to it.  A smart, handsome, if flawed, hero is defending an innocent man charged with murder.  The intrigue is compounded by the dramatic tension of the hero's strange condition: the automatic walking.  When it recurs, he finds himself walking across a bridge into Brooklyn.  A mysterious stranger approaches him and taunts him with what might be the murder weapon.  This would be an invaluable piece of evidence for his client and possibly even exhonerating.  But he is unable to stop walking, and leaves the stranger behind. 

The second half of the novel, however, is a suprising shift from the quasi-detective story into the final, fatal years of walking.  Some, but not all, of the details and facts of the first half are called into question: how much of it was fantasy, how much of it was hallucination, how much of it was real?  But it also changes the stakes of the novel, from the thrilling, glamorous intrigue promised by noir to the poignant, difficult challenges of everyday life. The noiresque first half mentions the disappointments of everyday marriage and parenthood - the frictions, the weariness - but these just heighten the sense of escapism; we look to the drama of the lawyer-detective narrative to get away from all this.  In the second half, we begin to realize the cost of escapism and of taking life for granted, and the book turns towards a fuller investigation of love and commitment.  

One particular question drives the first half of the book, "Is he mad or is this condition real?" The question is rehashed continuously, and takes on the perserverative quality of a detective insistently seeking to find out whether the culprit is innocent or guilty.  Here, we encounter familiar, if superficial, lists of the types of experiences a well-to-do patient with an unknown illness might face: multiple doctors, homeopaths, psychiatrists, belligerent and unforgiving colleagues, an article in the New England Journal of Medicine.  Curiously, the most obvious model for this type of condition, the famous fugue states of nineteenth century madness, is not mentioned.  But, these lines of inquiry turn out to be as unreliable as the first half of the book itself: as the walking condition takes over, these questions become less and less relevant; the truth is not black-and-white, innocent or guilty.  

His wife Jane's alcoholism and the cancer that eventually kills her (also not named: cancer is so often ascribed a place in the body as though it belongs there, as though we can understand  through its location) do not get the sort of attention Tim's walking does.  Becka, their daughter, seems to strive to come to life as an overweight child, a hipster, and eventually a mother herself, barely penetrating the surface of the novel: but then this is a novel about an overwhelming experience that usurps Tim's life. 

How Ferris compellingly conveys these walking episodes draws the reader into them as something more than an identifiable condition.  Indeed, given how taking things for granted is a theme of the book, an underlying point is that naming something allows us to take it for granted.  Naming may indicate mastery and comprehension, but it may also lead to a type of fugue state itself.  So, for example, in one of his compelled walks Tim stops off to buy a book of bird identifications; he does not keep it, he throws it out.  Later, he learns to appreciate 'the twitchy burrower with the black-tipped tail that scanned an upland prairie for danger . . . he knew it as well as the rapsy grass with the flowering spike that left soft yellow pollen on his pant legs, and he knew it as well as the bright constellation that suddenly resolved itself out of a confusion of stars.  He knew fee-bee fee-boo, fee-bee fee-boo came from a small bird with brushed gray wings and a tail as firm as a tongue depressor . . . '[306]