the thing with the resizing of the cover works fine - THX!!
another idea: what about a random filling (numbers/letters) of the identifier field, if it's empty (or a button for generating from some other thngs).
Because it's possible to get problems, if the field is filled with the same code - can happen, when you convert epubs by batch with atlantis word processor. the program fills the field with a date-time-code - but unfortunately it can happen when the books are small enough, that the code is in two books the same - and then some readers have problems with these books...
and the filed ISBN - can it replace the Type or Format? I think it's more used... (or can it used addditionally?)