[gm139]

I have a kindle paperwhite and I use calibre to convert books.

I noticed this:

1 - If the conversion process produces a directory containing:
a) the book in azw3 format
b) a .sdr subdirectory containing two files named as the book with
.azw3r .azw3f extension
everything works and my kindle recognize the book.

2 - If the conversion process produces a directory containing:
a) the book in azw3 format
b) a .sdr subdirectory containing just one file named as the book with
.apnx extension
the kindle does not show the book in the list of books

I do not understand why in some cases calibre generates format 1) in others format 2)

Any idea?