Aye,

This is a survival horror FPS game made in 2005 for XBox by Bethesda (2006 for PC Windows) in the style of Amnesia: The Dark Decent, which I'm sure you've heard of of. It's not so much a "shooter", as per the S in FPS, but more just a survival horror game where you sneak around and/or run away from bad guys. It also has the Amnesia esque mechanic of your character going completely bananas if you keep looking at freaky stuff too much; your vision and controls are affected, you start hallucinating, and you either need to go look at "calming things" (which usually means huddling in a well lit corner looking at the walls =P) or shoot morphine up the sleeve, the latter of which ofc is a method which has drawbacks if relied upon too much. You also need to use healing items to heal your injured body parts; you break your legs from falling from too high, you bleed from gunshot wounds etc etc. Even though this game is made by Bethesda, this one works very well without any 3rd party mods or the like, unlike some more recent Bethesda titles. As you already probably guessed or knew, this game is somewhat based on the Cthulhu novels written by H. P. Lovecraft, but it's not so faithful that it would completely spoil the experience of reading the books if you want to do that at some point. =) This one has a few attempts at longplayage on YouTube, but, as usual, they are somewhat rubbish as they are plagued by the usual drawbacks associated with most of newbie longplayers; subtitles are not turned on, volumes are not properly set (one Xbox longplayo had a huge stereo imbalance issue where everything was panned a lot to the right, which to me as a huge audiophile is a complete deal breaker), player skipping through readable text too fast, video being split into 15 min parts (seeing the loading screen every 15 min to me is a huge immersion breaker, especially with a horror game) etc etc. Cheers! =)

TL;DR
1) Turn on English subtitles
2) Adjust volumes properly
3) Take your time with the in-game readable texts
5) PC Windows version would be preferred over the XBox one, if you have a choice
4) Read the books because H. P. Lovecraft is awsome!

P-S. It does become a real "shooter" shooter at later stages of the game, though.