The Echo Maker (2006)

Richard Powers' new novel, a mad symphony on the fragility of human identity, begins when 27-year-old Mark Schluter crashes his truck on a rural Nebraska road. He awakens convinced that his sister Karin — a vulnerable woman, desperately attached to her only brother — is an imposter. Mark's condition — Capgras syndrome — brings to town an Oliver Sacks-like neurologist, who, after the flop of his latest book, is beginning to question his own carefully cultivated identity. There's far too much happening in The Echo Maker (an environmental kerfuffle, several romances, a mystery woman), but the chaotic novel is nonetheless one of the year's most engrossing.