[nhedgehog]

Thats very strange, I was guessing that the other books are left in memory but with your settings, there should have been a reboot inbetween.
Next try:
1) Is there something unusual with the filenames/folders you are using?
2) How many books are stored on the device?
3) Sometimes the device gets stuck while adding a specific book into the library. Sadly there is no message coming up if this is happening. Odd behaviour like that you are describing could be the result. Only way to find the culprit is to add the books in carefully aranged batches and see if and when the error is happening again.