THQ has yet to set a final release date to Metro 2033 follow-up Metro: Last Light, but the publisher has detailed the innards of the game's Limited Edition release in a morning press release. The highlight for many fans is the inclusion of Ranger Mode, a more "realistic" difficulty setting that was released as DLC for the previous game.
The Limited Edition package also includes a few other bonuses, such as the Ranger load-out (ie bonus currency to start with) and a modded AKS-74U. Last Light's Limited Edition release doesn't carry a higher price tag; it's simply a first-run printing upgrade that you'll be able to get either by pre-ordering the game or buying it shortly after release.
As an added bonus for PlayStation 3 users, those who pre-order the game on or after December 18, 2012 will receive a free Metro PSN theme immediately and a download of THQ's Homefront when Last Light launches.