Having been developed before Blizzard decided to focus exclusively on the Warcraft, Starcraft and Diablo franchises, Blackthorne is unlike anything else from the developer. It drops you into the boots of Kyle, a denim-clad cliché of everything teenaged boys imagined to be "cool" circa 1994, as he traverses an alien planet hoping to rescue hostages and look especially rad while blasting enemies to bits. While the story only exists to support the action, most won't care once they discover the "no look, behind the back" shotgun attack.
If any of this piqued your interest, why not download the game? Anyone with a Battle.net account is now able to pick up Blackthorne from Blizzard for the very attractive price of totally free. There are no caveats here; once you've downloaded the game, it's yours to keep.