I've found that my bookmarks disappear when a book is on the SD card so I always put the book I'm currently reading in internal memory.
I have just a little over 4 megs in my internal memory, but for some reason it reads only 233 kb available, which blocks me from adding another book. I've deleted and deleted and deleted with the only result that it went from 234 kb available to 233!! I'm on the 538 build and avoided the latest firmware updates (and the problems with same).
Anyone have any ideas I can get it to give me the 64 Megs of internal memory back?
Could there be some sort of hidden file hogging the memory?