I think they meant the physical device

https://www.kobo.com/ca/en

They can be a bit pricy if you’re young and on a budget.

If you’re trying to read on your phone only, I’d recommend these apps:

• Readest: The app is on both mobile and desktop, it’s a nice experience, and it’s free/ open source. I found it to be stable but I’ve seen comments about bugs: https://github.com/readest/readest
• Moon Reader: It’s paid / proprietary, but well known and customizable: https://play.google.com/store/apps/developer?id=Moon%2B&hl=en-US

As for sourcing the files

• see if your library does any digital lending
• check out free sources like Project Gutenberg and Internet Archive

Some comments brought up a home server, but you don’t really need that if you’re starting out with the hobby and it’s just for yourself. That’s more for managing large libraries of books and access by many users.