You will face, dispatch and sometimes run from a swathe of mutilated monstruosities, some being traditional zombies (in love with barbed wire), while others are towering creatures. There are even invisible enemies, which you can detect via footprints left behind, the rustling of nearby items, or doors opening or shutting down.
If you're expecting something that takes itself seriously, you're not going to find it here. It has that cheeze-fest, grindhouse appeal to it, and personally, I find it awesome when it goes over-the-top silly. Zombies with guns, manning turrets or driving cars, that's where this game shines.
Of course there's some challenge to all of them. Detective Castellano has these wide swings that don't always connect, and due to the awkwardness of the fighting, even a zombie might eat-you up in the early moments. Sure, you get stronger, as you gain more weapons including a revolver, shotgun, and even a crossbow that shoots spear-sized bolts, and level-up the character enough to take at least a few slaps across the face.
Slightly more difficult are the boss-battles, copy-pasted several times throughout the game, giving you plenty of time to first learn the fights, and then find them tedious and repetitive.
As I previously mentioned, mister Castellano is not your movie-type detective, taking on 5-6 individuals at once and surviving. He's kind of a wimp really. Fragile, weak, and able to sprint only for a few seconds. He can't take more than 4-5 bops to the face, and there's no such thing as regenerating health (there are health-packs scattered around, but they're pretty rare).
By finding green goo (in jars or puddles left behind by various creatures) you get to level up, improving his ability to carry more ammo, spring for another second, or maybe just another inch of life. Yet, with all these upgrades, you won't get anything more than a second chance. You will never feel like a god mowing down hundreds of shambling horrors, instead you'll just be able to run away more effectively when things get nasty.
So yah, The Evil Within is not scary, not one bit. At times it's tense and when it embraces the overall goofiness, it becomes entertaining. There's a certain sense of humor permeating the campaign, and it never goes away, even when your head is rolling on the floor.