If you haven't played it, why not? BUY IT NOW!!!
It's a medieval-esque rpg in which you (warrior/rogue/sorcerer) venture into the depths of the labyrinth in Tristram in an attempt to save the world from impending destruction after the release of the devil (diablo) into the mortal realm.
The game-play consists of point-and-click to move and attack, with keyboard shortcuts. Players may use melee weapons as well as ranged weapons, or spells - there is a great spell book for the player to choose from, ranging from damage spells, to teleportation.