This is a game with the spirit of the classic RPGs but a modern design and technology. So far I love it and I highly recommend it.

Gameplay

This is where Divinity: Original Sin really shines the most, in my opinion.
There is a very interesting system that makes elements interact with each other. Is your character burning or reluctant to pass through a flake of poison? Cast a rain spell to dissipate these elements. But beware, everybody will become wet and thus will be more vulnerable to air and water spell. That means they can get frozen or electrified (stunned) more easily.
The engine also allows stuff like action happening in different places with different characters simultaneously. For example, you could split your party in two to attempt a flanking manoeuvre, or solve a puzzle that requires multiple actions at the same time.
Coop is great in this game. You can play with a friend, and not only you can take advantage of the two points aforementioned, but you also have a coop dialogue system. You and your friend (or stranger) play one of the two main characters, and you don't have to agree on everything. You can resolve conflicts with your charisma stat and a rock paper scissor game. Depending on the sentences you choose, you will get attributes points, like Compassionate or Heartless, which will give you opposite bonuses. So choose well.

Graphics

The game is quite sexy and is above the average for such RPGs. You can zoom and tumble the camera to see it better, and apart from a few blurry rock textures here and there, I have nothing to criticize. The effects of the elements in combat are quite beautiful, for instance the reflections when a surface is frozen. But don't get too distracted or you might slip on the ice.

Sound

The music is generally good, sometimes original and the themes are quite memorable. I can remember some of the tunes when not playing the game.There are voice overs and they are of good quality as well (can't say for other languages though). The sounds effects are good to very good. The ambient sounds really help to bring you more immersion.

Story / Writing

Although English is not my native language, I can say that the writing is really good. The language there is quite elevated, and it's pleasant to read.
There is a lot of humor, and characters have some depth, even the cheese merchant with his cheesy pick up lines :)
The Story is good so far, although not super original (you're gonna save the world once again). But the quests and dialogues, coupled with the graphics, sound and gameplay, are good enough to guaranty a total immersion and many hours of enjoyable gameplay (even more if you can bring a friend along).

There is also a level editor shipping with the game, so keep an eye for (potentially awesome) player content in the future.