Kimon

Well, pretty much what it says in the title. I can find a list of calibre-compatible formats, but most vendors are not specifying the format until after you buy the ebook. Also, I have no idea if some of them put in some anti-piracy protections that make it only readable by their specific program. I just want to be sure I can read my ebook; I once had troubles opening one, and since then I've been super suspicious