Angband is a freeware role-playing game based loosely on the books of J.R.R.Tolkien.
This means there's plenty of action in dungeons, encounters with monsters and a lot of bloodletting until you finally face Morgoth - 'The Dark Enemy'. Angbad takes some time getting into (like a Tolkien novel) but when you do the rewards are considerable. Its developer warns that it will virtually take over your life, although that seems a bit far fetched - it's well presented and there's plenty of depth but it's no World of Warcraft.
The problem is that Angband originally started life as a text-based game and has only recently evolved into a graphics-based game with sound effects. This means that the graphics are considerably behind what you'd hope for from a game based on books of the imagination of Tolkien but that doesn't take away from the fact that it's a very well put-together role playing game.
If you're a Tolkien fan and love role playing games, then you'll probably get a lot of hours out of Angband.