The Witcher 2 Assassins of Kings is a sequel and the second game in the series after The Witcher original. The game has been developed by CD Projekt Red and would be published by Atari in North America. The game is currently under heavy development and will release on May 17 if the development is over by that. The game uses the RED Engine to display powerful graphics and animations. Once the development is over, the game would be available in retail as well as digital versions. The Witcher 2 demo version is also confirmed to release but only after the full game launch.
This game is quite different from the previous one. First of all, it uses totally different gaming engine developed from scratch by CD Projekt Red itself. The Witcher 2 Assassins of Kings incorporates many features from the previous game but with tons of improvements to them. It features all new dialogue, enhanced graphical improvements, smarter AI and dynamic gameplay. This role playing game depicts non linear plot. Combat has been improved to the extent possible and the new tactic system guarantees more possibilities than ever. Visuals have been stunning. I bet you will be impressed when you see the game visuals. The game consists of different characters and levels but all those details are not available publically yet.
Regarding The Witcher 2 demo, it has been confirmed to release. You no need to worry about not getting The Witcher 2 demo version but the thing is that it is possible only after full game release. The full version is releasing on May 17, so you will get The Witcher 2 demo only after that. Pre-game demo is not possible because of the heavy development load. You can check more about The Witcher 2 demo here. ( http://tw2.thewitcher.com/forum/index.php?topic=30968.0 )