Singularity is something of an underappreciated FPS from a somewhat underappreciated developer. Having already put out classics like Heretic, Hexen and Jedi Knight II, Raven again went on a solo effort with Singularity in 2010 and it was largely deemed 'pretty good' by reviewers. However, I think it's much more than that. Although hamstringed a little by a few modern FPS conventions, Singularity does a great job of feeling like a classic shooter, ending up somewhere awkward between Serious Sam and Call of Duty.
To its merit however, the enemies are smart and strong despite being a little cliché, the weapons all have a lot of punch and character, even if they're a machine gun, shotgun, sniper rifle, etc. and there's many secrets, upgrades and places to explore despite being a mostly linear game. In short, Raven seemed to want to make this game much more than the sum of its parts, and in my eyes, they completely succeeded. The time manipulation mechanic, despite being vital to progress, seems more like icing on the cake than a core game mechanic however, so don't expect anything more spectacular than an amazing FPS with some additional superpowers!
Average Game Length? I took around 8 hours to get through the story on the hardest setting, it could take more or less depending on your skill or desire to be a completionist.
A Bit Like? TimeShift, BioShock
Is It Fun? The TMD provides some serious fun, the story is engaging and the weapons make mincemeat out of your enemies, a big yes.
Worth The Price? £14.99 is pretty much half the price of a retail title, fitting considering you'll be lucky to get a multiplayer game going given the game's age and lack of popularity. For the price, the solo campaign is more than worth it although consider carefully that that's all you'll be getting out of it if you're on the fence.