This game will draw you in, but will it keep you there? Just try to keep up.
There are a lot of heavily story related plot twists and items and many other things. Simply put, the game wants you to beat the living crap out of it without too much difficulty. You can't actually 'die' per se. Instead you 'die', and then you are revived at these things called vita-chambers. There are so many of these throughout the game that even if you do 'die', you're only set back a couple of rooms. As another effect, you really can't get lost. There is such a large amount of hints and stuff, that if you are actually able to get lost, you deserve a nice slp to the face. If that weren't enough, each enemy can easily be beaten, granted you've researched them enough (yes, as in taken enough pictures, you'll see what I mean if you buy the game and play it long enough). Now, what about weapons?
You have a fairly standard set of FPS weapons including a shotgun, a machine gun (tommy gun at that), and pistol. On top of that, you gain some not so standard weapons, this means flamethrowers, crossbow, wrenches, and plasmids. Plasmids are essentially what many TES fans will call spells, each of which performs a unique function and effect. However, at the end of the game, my absolute favorite weapon is... the wrench. This thing PWNS. You can't upgrade it, but once you have enough tonics and **** for it, it's like the damn energy sword in Halo. Sure it can't kill Big Daddies in one hit, let alone easily, but it can still pwn the living hell out of them. I actually rarely use my weapons any more now that I've got my trusty wrench so readily available. Beyond that, all other weapons are fully upgradable.
As for achievements, well, you shouldn't play the game for achievements, otherwise, you'll be selling it quickly. I've played it for about three days, and I already have about 810 GS off of it. Most of the major ones are story related and thusly impossible to miss. Some are for upgrading weapons, and others are merely for research (not worth much so don't go out o your way to get those).
Otherwise great game.