At first, I simply pre-ordered the game until release date. Subsequently, I simply just click Get the Code and it'll automatically provide you Steam code for Steam Activation and it works all across US, CA, Europe, and other region.
Other thoughts: File size is 47GB so make sure you have sufficient space to install games in SSD for faster game loading time as well as minimizing stutter. Game, however, still requires at least 4GB Video Memory to store high resolution textures, otherwise cause the game to hitch/stutter. Other than that, it's cheaper in cdkeys.com and I recommend Steam users to visit this website to save some money for other games to pre-purchase upcoming game titles in lower cost.