One note: Watch out for WinSCP -
If it thinks it is copying a text file it will change the line endings from Unix to Windows for you.
Look in your USBstorage/documents directory -
For a book or document you will find both a book name and a directory with the same name.
Using the 'delete' on-screen function only deletes the book name, not the directory. Manually delete the directory yourself.
The leaving behind of the directory is designed in -
That allows the firmware to send your annotations, bookmarks and reading times to Amazon, even after you deleted the book.