The idea is to push six of your opponent's marbles off the board, which you do by having more of your marbles in a row than he does. Conversely, you want to split up your opponent's forces as much as possible. Abalone comes with marbles for two players, but can be played with up to six with expansion sets. It works best with two or three players. I think this is a good game.
Players draw seven Scrabble-style tiles with a grid location on each from a bag.
Each turn consists of playing a tile at its grid location and drawing a new one. When a player places two tiles next to each other, he creates a hotel chain, and gets a free piece of stock in that hotel. Then, players can buy stock in existing hotels. But it may be worth keeping, since the defunct hotel can be re-created later on. It's a solid, simple game.