On the island, he develops this unnerving ability to paint, having done nothing but doodle before. After a while though, Freemantle starts to wonder if the accident unleashed some latent ability he had (he paints when he gets phantom pains in his arm), or if something is being channeled through him by an other worldly power.
Now I'm a pretty big fan of Stephen King and have been reading his books for years. Maybe it's because of this that I found myself thinking back to previous King books when I was trying to work out what was going on in this one. The isolation of the book reminded me of The Shining, and made me wonder if the elements King used in that book could be being recycled here. Other King books that I considered include The Dead Zone (and its relationship between brain damage and precognition(?)), a short story in Skeleton Key (about a computer that brought things to life). What I landed on eventually though was The Regulators a book he wrote under the pseudonym Richard Backman. That book is about an autistic child who is befriended by a demon, who subsequently uses the "strange wiring" in the child's brain for evil. The first chapter of that book is about as good an example "what the heck's going on here?" style horror that I've ever read. Sadly nothing similar was present in this book.
If you liked that book (which I did mostly) or haven't read it, you'll probably like this book. If you didn't like the book though you might get a little infuriated by the fact he (to my mind at least) lifted the essence of the story (if not the story itself) and inserted it into this book.