If you read books on an Amazon Kindle, you should know you can access all of your books on the web, too.
It keeps in sync with your Kindle device and any Kindle apps you might be using.
While it’s not as comfortable as reading with e-ink display, I like it because I take a lot of notes in my books. Typing on the e-ink display of my kindle sucks, and my phone is only marginally better. Being able to rattle off a longer note is so helpful, especially if you’re syncing your highlights and notes with something like Readwise.
When reading a book I’ll hop back and forth across devices, using whatever is at hand so I can always get a few more pages in.