First, if you have trouble running the game do NOT install a shader, they will reduce your framerate anywhere between 2-20 fps based on how many effects are turned on and running. Never talk about modding the game in-game.

Shaders will do everything from injecting higher end sharpening and anti-aliasing, to adding eye adaptation and depth of field, to even making the game look cel-shaded, all entirely on how they're configured.

You can even make it look like an 8mm film.
Comparison before and after.
Walking towards Antitower feels a little more magical when you bring out its colour.

Installing of a shader is easy, it'll download in a zip and you should extract the files to your game folder so that the dxgi.dll file is in the same place as your games executable.

You can disable the shader by renaming the dxgi.dll (for example, dxgiOFF.dll). And you can uninstall it as easy as deleting the dxgi.dll and any other files that came with the shader.

Configuring your own shader is a harder, longer process full of tweaking numbers in lines of code to get the effect you want and isn't recommended for beginners.

However you can find a database of preconfigurations at this location. You can also find my personal configuration here. My personal one can be toggled on and off ingame with F11.

Important: When using a shader, pressing print screen will take TWO screenshots. The game itself will take its own screenshot WITHOUT the shader effect, this can be found in your default screenshot folder. The shader will take a screenshot WITH the effect, and this will be found in your game folder, in the same spot the dxdi.dll is.

Using the Steam overlay to screenshot with F12 will also not capture the shader effect, the screenshot has to be taken with the shader. However you can move the pictures to the Steam screenshot folder if you wish to upload them to Steam (you must make them a jpg first).