You can get through a single town in one sitting, making it one of those perfect games to play when you've got a half hour or so handy. Many times, that "half hour" turns into far longer, which is really the best compliment I can give a game.
If you're looking for something much more different from a typical hack-and-slash RPG and want plenty of challenge, Din's Curse and its expansion, Demon War, will be sure to sate your appetite for a long, long time.
Just like Din's Curse, Demon War is fun, but I still recommend it in small doses. The action tends to get repetitive after 4-5 towns and, if you're no collector of sets and rare items, you won't find many interesting rewards in the idea of endlessly killing brainless monsters; not to mention that the dynamic side of the world can frustrate less patient players. So if you don't get along with the idea that in a game you get random, uncontrollable events that are out of your influence (just like in real life), then Demon War won't keep you interested for too long.
With 190 different ways to combine your character, many monsters and a dynamic world map "in's Curse: Demon War is very diversified. But the Graphics and the Quest-system isn't fully and nice developed.
Demon War isn't the greatest expansion I've seen to a game like this, but it's certainly something. It capitalizes on the strengths of Din's Curse and its unique properties, building upon them and adding more properties of that kind to the game, instead of just adding more enemies or something (though there are more of those). Like the original game, if you want something different in your dungeon delving, something else that just isn't on the market, Din's Curse, and now its expansion, will be perfect for you.