If you're a fan of the gameplay of Skyrim, Enderal is a great place to go looking for more. It features a large map with varied biomes, and lots of interesting dungeons to visit with small internal stories matching up to Bethesda's best. Furthermore, the character progression system and combat is great fun.
Music and voice acting is similarly great -- I'm in particular a fan of the track that plays in the snowy regions. It's also clear that the developers had mastered the scripting of the engine, and many quests feature impressive setpieces.
Most of the story in the game is in the main quest, and here I'm regrettably not a fan. In short, it feels like the writer wanted to tell a bleak story with themes of loss and inevitability. Since your character -- in typical Skyrim fashion -- ends up being an avatar of destruction in gameplay, the game has to jump through a lot of hoops to explain why the problems you're facing can't be solved through combat. Some of these solutions are elegant, but a lot of them are stupid. The finale was perhaps the best example of this. After the ending, it felt like as if the game had presented a locked room murder mystery, and then gleefully revealed that the murderer was capable of teleporting. Lovely.
However, there is one story which I felt succeeded at basically every point the main quest failed: the Rhalâta questline added by Forgotten Stories. It presents a villain that, while mysterious, has much clearer capabilities and that can be outsmarted -- to an extent -- by the player. The main side character Tharaêl is also integral to the plot, as opposed to the Bioware style romance targets in the main quest. The questline features both fun gameplay and a story that reacts to player action, like a true RPG should.
All that being said, it's a free mod. I hated the main story, but it tries and fails at doing something spectacular, which is in itself interesting. It's worth playing.