The Raw Shark Texts. Steven Hall by Steven Hall

Eric Sanderson wakes up in a house one day with no idea who or where he is. Instructed by a mysterious note to visit a Dr. Randle, Eric learns that the agony of losing the love of his life in a scuba-diving accident three years before has destroyed his memory. As Eric begins to examine letters and papers left in the house by 'the first Eric Sanderson,' a staggeringly different explanation for what is happening to Eric emerges, and he embarks on a quest to recover the truth and escape the remorseless predatory forces that threatens to devour him.