Hi Nicola, The book directory is "e_book". Just putting that on your card should be enough. The complete list of directories (excluding any files) looks like this.

.
|-- e_audio
|   `-- e_record
|-- e_book
|-- e_image
|   `-- e_screen
|-- e_note
|-- e_notepad
|-- hwsys
|   |-- hwdb
|   |-- hwidx
|   `-- temp
`-- temp

If you go into the settings menu, on page 3 there's the option to reset to factory default and / or clear all temporary files. I don't know if that will help recreate the filesystem. There's also a reset button on the back, but I guess that just resets the hardware - not the SD card. Hope the above is useful. T