here's a book that makes koreader crash when I convert the azw to epub in calibre. (firefox epub plug in opens it, sigil too)
DL
http://demo.ovh.eu/en/d0e83364c745075057b9d71896e8c801/
I converted the azw to mobi and koreader opens it now. Using FW 3.15 and nightly 2014.11.271