FBReader uses CSS from the document by default; you can turn it off in, IIRC, four stages. KOreader gives you more control but in a less friendly manner: in ad

FBReader uses CSS from the document by default; you can turn it off in, IIRC, four stages. KOreader gives you more control but in a less friendly manner: in addition to choosing specific CSS from several supplied files, you can write your own. (Also wins for KOreader: excellent OPDS support, and easy self-hosted sync server.)