I just tried it with 45 books
I used Save to disk (EPUB) /single folder
with cover as a separate file (this is set in Preferences) so all the photos have a title/author
My device ignores the books but you could use the command prompt
DO NOT USE ON YOUR LIBRARY
Code:
E: (the drive letter for the sdcard)
del /S *.epub <this walks the sub folders
to get rid of the books