The Troop by Nick Cutter.
King wrote that this book was old school horror that scared the hell out of him. Based on that blurb and other people's ravings about the book I decided to give it a read. While reading this book I couldn't help but think back to Cronenberg films such as They Came From Within or The Fly. The Troop is body horror at its finest. I'm interested in reading other works by the author now. Canadian Scoutmaster Tim Riggs and his five teen Boy Scouts are on a wilderness camping trip to a small deserted island, one that will allow Riggs' charges a chance to put their outdoors skills to the test and of course gain more scouting patches.On the first night of the troop's trip to Falstaff Island a sick man who is almost skeletal and very hungry shows up and joins them. As a doctor, Riggs feels compelled to try to assist the man. That proves to be an unwise move. If you don't like gore or body horror this is very much not the book for you.

The difference between this story and similar gory tales in a crowded marketplace is that the author, like King, makes some very realistic, if not always sympathetic, characters. You care about what happens to the troop. This wasn't a short book but it was one which was hard to put down.