I'm looking for something dark, atmospheric, ambient, preferably little to no drums or vocals.

a track that comes to mind is "Rundgang um die transzendentale Säule der Singularität" by Burzum.

Repetitive, dark.... you get the idea, just need something to listen to while I read lol

MDP-Emptiness is something I was given recently. Vocals are quite sick and remind me of a dying orc screaming. Drums are pretty minimalistic except for a few tracks which provide normal repetitive black metal blast beat. The production isnt all that great but it works great for this album in my opinion.

Similar to this would also be Lurker of Chalice s/t. A side project by Wrest, creator of Leviathan. This would probably be my favorite of the two but I recommend MDP first because I feel it better suites your request.

try the most obvious, "easy" ones first (before going to the darker realms of ambient, hehe). stuff like old Mortiis (up to and incl. "The Stargate"), Wongraven should do fine. After that take a look at the backcatalogue of the Cold Meat Industry label (though there are also tons of more noisy stuff you will sure find also a lot to listen to in the background while reading)

Peordh "Glaring From Spacious Woods and Mountains of Eternal Frost"

Have you listened to any Martial stuff? A Challenge of Honour and Karjalan Sissit are golden.

Wongraven

Za Frûmi from Sweden create dark ambient Orcish soundscapes from Middle-Earth. The vocals are said to be in the Orcs' Black Speech.

Early Forest Silence