I didn't noticed before that accented chars are sorted last which makes the alphabetical order a bit confusing.
So Amos Oz is listed before Kenzaburo Oé, I don't know if the sorting is looking only at the ASCII code of the letter but I'd say that for most languages the following should be true while sorting:
Code:
a = á = à
e = é = è
i = í = ì
o = ò = ó
u = ú =ù
In this day of Unicode and with calibre localized to different languages I am quite surprised since I imagine Python would have support libraries for all kinds of international / unicode sorting
