Not botanical, but I use KOReader on a Kobo Clara HD (the same screen as the Paperwhite, if I recall correctly), and am happy with it except for the arrangement; covers don't show, and sort-by-title didn't work last time I tried. It's currently by author, which would make sense if I knew enough author names along with their books. I'm sure there's a way to get these things working, I just haven't put the time in yet.