it really depends on mood,
but i find IDM, post-rock, or maybe even shoegaze to work pretty well for reading books/studying, here are some suggestions which also includes those genres as well as indie rock, new-age, ect.
air
tortoise
supersilent
boards of canada
caribou
denison witmer
mono
kraftwerk
spiritualized
m83
oval
pole
patrick o' hearn
my bloody valentine
stars of the lid
john serrie
grails
below the sea
bright red paper
the evpatoria report
f.s. blumm
stars
20 minute loop
john vanderslice