Brilliant! Simple, yet structured enough to keep the game interesting. If you like The Black Hack (and usage dice for resources) and have an interest in Cthulhu Mythos (or want to learn more about it), buying this book should be a no-brainer. It contains a well written primer on Cthulhu Mythos for the uninitiated. The rules also make converting adventures from other rulesets very simple (all you need for antagonists is Hit Die, and if the adventure you're using doesn't have HD, dividing an NPC's HP by 6 and round up for a HD number works well).
[5 of 5 Stars!]