Stuff like Serious Sam, Painkiller and Doom is being mentioned in this thread, but actually, I'd say that none of the comparisons is valid, since Necrovision's focus is not entirely on shooting - you'll be killing stuff in melee as often (if not even more often) than in range, which is somehow refreshing.
Levels are varied nicely, you start in WW1 trenches, then go through german-occupied old citadels, later on you're put into some weird ancient dungeons/temples (although one level here was suffering from SERIOUS copypasta) and end up in hell, and the art design looks pretty too. There are twelve levels, each taking ~45 minutes to complete. If you want more, there's also a 'challenge mode', in which new levels unlock after finishing the single player missions, and they involve shootemups like 'blow up 100 zombies with the grenade launcher'.
Difficulty is well-adjusted too, when you get bumrushed by large numbers of shitty enemies you'll be in quite a bit of trouble, and 'uber enemies' (that spawn rarely and of which there are 2-3 kinds) soak up a lot of damage and pack a punch. There's not that much of a big number of enemy types, but the gameplay doesn't suffer from that really, because they all do what they should do - zombies shamble to you and try to rip your innards out, ZE GERMANZ either sit tight and try to snipe you with rifles/submachineguns or charge you with bayonets, some are heavily armoured with fulltime machine guns and they act like 'tanks' (regular tanks also appear from time to time), fast zombies chase you and try to rip your innards out, etc.
What I also liked was how the gameplay turns a 180 degrees somewhere around the middle. In the first part you run around trenches shooping ZE GERMANZ and some occasional zombies with normal weaponry, while in the second part you are put inside vast, ancient underground compounds where you battle vampires, lotsa barbed-wire-covered zombies, spiders in gasmasks and other supernatural stuff. The normal weapons also get changed for the 'shadow hand' (which is FUCKING AWESOME) - it's a wolverine type spiked gauntlet with three different firing modes and regular slashing - and 'vampire weaponry' which is basically, an smg, a shotgun, a grenade launcher and a flamethrower wielded in one hand so you can use them at the same time as the gauntlet. You can also resurrect fallen enemies to do your bidding, but that's pretty useless. Later on, you can also pilot a dragon (although that level is kind of boring in the long run), and a generic mech with a chaingun in one hand and a rocket launcher in the other (of course with unlimited ammo).
Moreover, the game rewards creativity with its special attacks and comboes. Each of these does a lot more damage than regular attacks and loads up your level of adrenaline (which fuels the gauntlet's special attacks, and allows bullet time if activated), and there's really a lot of them. For example, ONLY with the regular rifle you can do as follows: stab twice with the bayonet for a 'doublestab' special attack, stab in the head for an 'impalement' instakill, stab and shoot, charge + punch + shoot, shoot + kick, and probably more that I've forgotten about, and there are many other weapons, each with unique comboes, which really adds a lot of variety to the killing.
The "BLAHBLAHBLAH" factor is also very low. If you couldn't give a flying crap about any actual 'story', you should be satisfied, as there are maybe... 4-5 places where you have to wait and listen to people yapping about demons, destiny and all kinds of stuff like that, while other spoken parts are being done when you are running around and shooping and there are cancellable 'slideshows' after each mission that give you additional insight into the story.
Definitely recommended.
