I first played Tales of Maj'Eyal about a year ago, and was recently inspired to pick it up again due to a recent expansion. (Which I haven't played yet - might write some more about the expansion after I've spent some time with it.) It's free to play, but there are expansions to purchase and benefits for those who donate to support the developer. Both of which I have done, because supporting this kind of craftsmanship is well worth doing.
roguelike, using the same turn-based dungeon-crawling gameplay of classics like Angband, NetHack, and of course the original Rogue. Though unlike its precursors, this game has some decent artwork and sound. It won't burn up your graphics card, but it beats ascii maps! For the most part, you're moving your character around a map and fighting whatever you bump into. Sounds simple, but a rich variety of player skills and enemy types keeps it interesting for a good long time.
There's an entire high-fantasy mythology underlying the world, and plenty of characters and quests for your character to handle. While the general arc of the campaign is always the same, each level is procedurally-generated for each game, so it's never quite the same as you play different characters. Making it through the whole storyline without dying takes some significant effort, as with most roguelike games, so it's good that there are options to allow continuation after death. Of course, if you'd rather play classic perma-death, there's that option too.
Tales of Maj'Eyal is definitely meant to be played more than once. There are some classes and races that can't even be played when you first start up the game. As you move through the world, certain discoveries will unlock additional play options. Steam says I played 99 hours (before the latest expansion) and I know there's some bits I still have yet to unlock.
My favorite part of the game is the wide variety of characters that you can choose to play. Multiple types of magic users, different warrior classes, various types of rogues, even undead characters - there's a ton of different options. Different parts of the game are easier for some types, and more difficult for others. The game feels different with each new character.
There's no multiplayer aspect to Tales of Maj'Eyal, but that doesn't mean there's no community. When you play while connected to the game server, you can chat with other players and see updates of what is happening to others. Most of those updates are either players dying or gaining achievements - more the former than the latter, most of the time. In addition, the game master (who goes by the handle DarkGod) will occasionally give out bonus items or open portals to special zones, such as the Bearscape (guess what...it's all bears). Watching that constant feed of deaths and accomplishments and exploring those bonus zones are fun extras.
Now that I've started playing Tales of Maj'Eyal again, I expect it'll be a few dozen more hours of gameplay before I put it down again. Not only is there plenty of world to explore, but there's always just one more character race/class to try...