Grand Theft Auto IV hasn't been supported very well since GTA V took the spotlight, but there's still a hardcore fanbase for the game. Sadly, the game dissapeared from Steam last month due to the API for Games for Windows Live finally closing down. Rockstar never bothered to patch Games for Windows Live out, which made even getting the game to run trying.
The good news is, Rockstar have come good and re-released the game to Steam with some improvements. Firstly, Games for Windows Live has FINALLY been stripped from the game, which makes it, y'know, actually playable on Operating Systems released after 2009.
Even better is if you owned just Grand Theft Auto IV, or Liberty City Stories, you now have the whole sega combined, for free. These have both been merged into what is now known as the "Complete Edition", meaning you can enjoy the whole game plus DLC without having to install the entire game twice onto your hard drive, which was kinda crazy.
The bad news is multiplayer is now gone, as it's now been removed along with online leaderboards. That's not a huge loss though, as GTA Online is the far superior experience. Sadly, RamJam FM, Self-Actualization FM and Vice City FM, which belonged to the Liberty City Stories, are also now removed.
If you own either of these games, you'll already be upgraded to The Complete Edition today. The Complete Edition itself goes on sale on Steam and Rockstar Games Launcher next week, on the 24th of March.