As nice as this deal is, i already own it. But does anyone know if you can buy these games then add them to your inventory? Or do you only get a key... since i don't think keys can be added directly to steam inventorys.
No, you can't add keys for games you already own to your Steam Inventory. The only way to do that is to buy an additional copy through Steam.
A shame really, since that would be a pretty useful feature.
And, to make things even more compicated, Amazon "overrides" the current code if you buy a game again (at least with some games).