Nightmare Reaper is a pretty dang cool roguelite looter-shooter retro FPS

pcgamer.com:

Sitting somewhere between a modern roguelite and a retro FPS, Nightmare Reaper is a recent release from indie studio Blazing Bit Games that combines familiar elements into a formula that feels quite fresh. Putting you up against hordes of monsters that explode into fountains of gore, Nightmare Reaper takes open-ended levels both procedural and handmade and lets you tackle them however you please—as long as however you please involves using 80-some weapons with all kinds of weird random modifiers to blow everything up.

I'm a big fan of the weapon that's a book which shoots lightning bolts.

As you go through levels, you pick up new random weapons and showers of golden coins. Those coins can be used to buy character upgrades and abilities through minigames that you play on what appears to be a Nintendo Game Boy Advance SP. That's either nostalgia or absolute confusion for you, I'm sure, but it's a weird little stylistic touch that lets you know precisely where Nightmare Reaper is coming from.

You can find Nightmare Reaper on Steam and on GOG.