I've installed it and have been playing it for a week or so. txa's review is spot on. The primary twist to the action game is the attunement system. Almost every item in the game, gems excluded, has an attunement that can be unlocked. Kult encourages you to be a jack of all trades, as specializing in one type of combat doesn't make you better at it. For instance, you can choose heavy armor attunements that will make you decent at wearing armor and you'll get bonuses. However, you'll only find the next better attunement at the same rate as all other attunements. You can't go buy and attune Heavy Armor 1, 2, and 3 from the beginning. It will be on found loot or in stores as you progress in the game. However, let's say you play on normal your first game and open up the whole world. If you started over then the whole map is open with the next character, not sure if this is a bug, so you could then skip heavy 1, 2, and just go to where Heavy 3 items are sold and gear up
As a guy who loves the attunement system, I enjoy swapping out depending on the groups of monsters I'll be facing. If I know that a certain monster is very tough but slow, I'll equip fast weapons and a speed attunement and perhaps a bow to whittle them down before they get to me. The guy who posted about escaping to the dream world is correct,
BUT, you don't know what's on the other side when you switch. In later maps, the dreamworld has very fast flying creatures that will swarm you when you arrive. If you're in their area of the map when you cross over, you'll be reloading.
This is a very solid game, much better than most action crpgs. Not as good as Divine Divinity, but better than Legends of Dawn or the Blades of Destiny remake. If you haven't played Kult yet and are looking for a solid game, this is a good bet. You will have to either dual boot or follow my guidelines above. I find alt-tabbing sometimes works and sometimes doesn't. Always close all apps before opening Kult, but then you can generally tab out and open up Mozilla, Chrome, IE yuk, etc.
Here is a wonderful resource for Kult:
http://camilleb.home.xs4all.nl/Kult/