Question about PocketBook Touch HD 3

The purchased device comes with the two Polish e-book shops "Empik Go" and "Legimi".

The Pocketbook bookshop itself. However, you are free to choose where you buy the books. The book format (file type) must simply be one that works on the reader. Such a book bought somewhere can then be downloaded to the device either via your own e-mail address or via a Dropbox account.