I myself strive to store all my books in the reader.
Of course, I also store backups on other media.
I don’t use Dropbox because the free storage is small for me and I don’t want to buy more storage here either, as I already have storage elsewhere for this purpose (storage).
The reader's library can be stored in several languages at the same time, I use Hungarian and Polish sublibraries.
As for the library: books can be organized into folders, grouped by author, by topic, subdirectories can be managed, or as the user wants.
You can create any directory system you want.
As for the case: you might want to look around amazon.com, amazon.co.uk, and ebay.com, ebay.co.uk as well.
There are factory cases (pocketbook) and aftermarket cases such as kwmobile, I find the US origin Fintie case (
https://www.ebay.com/itm/FINTIE-Slim...EAAOSwOFRfx~tb). Wakes up, sleeps, light, thin.
Otherwise, I completely agree with the respondents in front of me, one of the best readers so far.