@nuukaset annas archive has a lot of crap epubs by way of someone just used calibre's pdf-to-epub tool and then they called it an epub. those are terrible epubs. the formatting is all fucked beyond recognition in those. i prefer just the PDF in that case.
k2pdfopt does a superior job reflowing (and koreader doinked the code from them for the "reflow" option that koreader now has) a pdf to fit the small screens.
(that being said if i had it to do over i'd probably have gotten the sage or somesth. the color screen model has shit contrast and i'd like the bigger screen

)