Articles:2016/02/05/Rise of the Tomb Raider First PC Update
The Windows and Steam versions of the game should automatically update when starting the game. The new version number is V1.0 build 610.1_64. You can check which version you are using by switching to windowed mode (press ALT+Enter simultaneously while in game) and taking a look at the window title bar. If it still reads 604, it is time to upgrade.
Among other problems Nvidia SLI and other graphics issues have been addressed. For a full list of changes see the Steam announcement.