To read the books in the Kindle app, you can download them within the app itself - look at "Archived" material, or sync new material (from memory). If you look in the Kindle Library folder it creates, you will see a lot of gibberish-named files and folders. If you are lucky, some of the books may download in a format Calibre can handle (.azw for example), but more likely, they will have the new kfx format - have a look at the sticky here
https://www.mobileread.com/forums/sh...d.php?t=283371
to see how to get round that.
Depending what you want to do with your books, you may also need apprentice Alf's help too (google him)
Hope this helps
Liz
(oops, parallel post, but you CAN read them without a physical kindle device)