You don't have to be a genius to play this game, but you will have to use any reserve of cleverness you might have to win.
The rules are a bit counterintuitive: Each player tries to get as many points as possible using double hex color tiles (two hexagons joined on one side), laying them down one-at-a-time on their turn. There are six colors/symbols on the pieces, and for each point obtained with a specific color you advance your scoring token one space for that column. At the end of the game the player with the most points in their least-scoring column wins the game.
Sound a bit complicated? It's not that bad. In fact, games typically last under an hour, and often under 1/2 hour. Play is dependent on other players more than on predetermined strategy, so you'll usually lay down tiles pretty quickly, though staying a course is important. If you adapt too much to what other players are doing, chances are you'll end up in last place.
Designer Reiner Knizia is a legend among gamers (especially in Germany) for his more than 500 published games and numerous awards. His staggering output isn't watered-down, either--each game is unique and logic-based. Would you expect anything less from a man with a Ph.D. in mathematics from the University of Ulm?
This isn't just cold logic. It is just logic, but Knizia's abstract game is highly addicting and more fun than many games with a lot more rules (probably because it doesn't have a lot of rules). Replay value is high, and while they might not pick up all the game's nuances (okay, they're sure not to), even young players will have pleny of fun balancing their points-acquisition with their tile placement.