This is one of the best OSR style rulesets I've played. It's bursting with useful tools for all sorts of adventures (including material for Solo play with no additional books). This is a real deal desert-island game right here. Enough material in between these covers to game for years and the author offers it for the low, low cost of FREE. The art is nice, the layout is compact and useful, it's B/X compatible.
You literally can't lose, get this game.