I found this book completely by chance at the library. I didn't have anything to read at the time and nothing was waiting on hold for me so I just walked up and down the aisles of hardcover books and found this one. The cover was different from any I'd seen lately and when I picked it up and read the first few lines I was hooked.
The story begins with Eric Sanderson waking up in a bedroom and recognizing nothing. Everything feels like it should be there, he had no fear or alarm, but also no memory of anything before waking up on the floor. He goes downstairs to find a note addressed to him...from himself. He has instructed himself to go to Dr. Randle for help, which he does, and to watch for more letters from The First Eric Sanderson. Dr. Randle informs him that he has a dissociative form of a fugue state in which he can't remember anything before his girlfriend's death three years ago, and with each 'awakening' he loses even more of his memory. The First Eric Sanderson tells him he is being stalked by a conceptual fish called a Ludovician. This conceptual shark feeds on ideas and will continue to stalk Eric and eat his memory unless precautions are taken.
Armed with precautions and preventative measures, Eric goes on a journey to find a doctor to help get rid of the Ludovician. He enters Un-Space (the forgotten bits of space behind bookshelves and whatnot that are connected in a vast underground network) with the help of a girl who has also been affected by a conceptual fish. They find the doctor who can help them and they build a boat to battle the Ludovician. This boat is made of concepts, ideas and beliefs and they build it in a room made of old phone books.
The entire story is told from Eric's perspective, the perspective of a man slowly going insane. It was a facinating read.