If you have a library card, most public libraries make their e-books available on line. If you don't have a library card, go get one and inquire about their on line checkout system. I read a lot of e-books and audiobooks through my library's on line system.
Good point. I was assuming Harry Potter wouldn't yet be available through those channels, but it's worth trying.
Copyrighted material. If there is such a site, there's going to be a fee for access.
... because they, in turn, have to pay for the use of the material.