Thanks to a deal between Warner Bros. Interactive and GOG.com, 2007's action shooter Stranglehold has returned to PC. Co-created by legendary Hong Kong director John Woo, Stranglehold serves as a sequel to his classic 1992 cop film Hard Boiled. Starring Chow Yun-Fat (who reprises his role in-game), the film and game are known for featuring some ridiculous action set-pieces and a disregard for physics.
As for why Stranglehold disappeared in the first place, it's likely the same reason any digital title does: expiration of copyright. Digital copyright laws are a strange, tangled web of mystery that most companies can't quite figure out. After licensing something for a set period of time, contracts expire and many games get delisted from digital marketplaces.
This has happened to even the biggest of publishers and developers. Rockstar Games has famously had to remove content -in the form of songs- from its Grand Theft Auto games to ensure their preservation on digital marketplaces. It seems various industries aren't willing to play ball with each other, which leads to perfectly fine titles going missing for a while.
As for whether or not you should grab Stranglehold, it wasn't that bad of a game. Its main claim to fame is having the backing of John Woo, but the shooter did resemble the older Max Payne titles quite a bit. At the time of its release, Max Payne 2 wasn't that far removed from the public consciousness. A sequel to that series wouldn't materialize for another five years, so anyone looking to get a fix of slow-mo bullet dodging wasn't left with many other options.
It also featured a standard multiplayer mode that let you dodge around as Chow Yun-Fat. That's certainly worth something, especially with how storied his career is. You'll probably not spend any time with the mode, but at least you can re-experience Officer Tequila's gamified take on Hong Kong cinema without resorting to piracy.
You can currently buy Stranglehold from GOG for $9.99. If you'd rather go the console route (the game was also released on PS3 and Xbox 360), cheap copies can be found for half that price. A special PS3 edition even includes Hard Boiled on the Blu-Ray.