I've never played a game named after a bone before, but was pleasantly surprised by what Tibia offered. The plot is not a whole not different from your standard role playing game. You're a knight, or a druid or a sorcerer or a paladin and must explore a mystical world solving quests and building up your skills and weapons.
There are plenty of zones to explore, although you'll only be able to access some of them if you're a Premium subscriber. The game is pretty easy to get into, even if you've never touched an MMORPG before. The inventory is quite straightforward to understand and the battle system is highly intuitive. Graphically, the game reminds me a lot of Ultima, which is no bad thing, because although it's colourful and detailed, Tibia doesn't put a massive strain on your system resources.
One of the few things that annoyed me about this game was the fact that you lose your skills, experience and even levels when you die, making it very frustrating having to build all this up again - only to lose it all over again.
As a result, Tibia is a highly enjoyable game if you have the patience to come back and build up your skills again whenever you die.