Rats in the Walls is the game I was waiting to play in the universe created by HP Lovecraft. It's a simple game, with a solid engine that's easy to pick up, but rich enough to play long campaigns. It's also a collection of very useful advises (the best I've read) to create and lead adventures inspired by HP Lovecraft stories. It is, finally, a short book, served by an effective layout and inspiring illustrations, which allows GMs to run great adventures without waiting. A total success!