Thanks RSanders for all the tips on this!
What I meant with saving things on SD cards was to make sure that if for some reason the Sony software stopped functioning (e.g. Sony decided to scrap the Reader, something I do worry about sometimes) one of course still wants to have the books that one bought from them available for reading. So having them stored on several SD cards would work then I guess, justg popping in the card in the Reader and the book would be there readable. No need for going through the software..... that was my thought anyhow
Zevs