@jimthing As I was told by an author, while Amazon now accepts epub files, they convert them to mobi files before putting them in the Kindle Store. I then have to use Calibre to convert them back to epub so I can upload them to my iPad Minis.
On the Mac, just double-click the epub. If Books is your default app for epub, that will import it. (Otherwise, Open With Books.) As long as Books is set to sync in iCloud, that will also copy it to your other devices.
you can use kobo. It is an app for reading. I usually email myself the epub file then go into the email where the file is located on the right hand side there will be 3 little dots click that to save and then go into the kobo app and click the phones menu button to import the epub files to your kobo app and then it should show up in your kobo library.
I was an early adopter of ebooks, in part because of my terrible eyesight, but mostly because I happened to break into reviewing just before the 2001 anthrax attacks. Fear of contaminated packages increased shipping time for cases of manuscripts from four days to forty. Electronic books (which in those long-ago days were really just doc files) provided instant gratification.
Paper books are durable along several axes. I have run across files only decades old whose archaic file formats are no longer readable by any machine I now own. Even before that, I lost files on floppy disks as the disks themselves degraded. Many of my paperbacks are approaching their first half century or only dimly remember it. I have hardcover books that are more than a century old. I have no problem reading them, provided only that I hold them close enough to my eye.