What site can I use to download books onto my iPhone for free?

I have the app 'iBooks' where I used to store all my books but my phone got wiped and now the site I used to use have taken down the books I'm looking for (Harry potter) the site I used to use is www.epubbud.com and now I can't find a website that is even a little like this.

Great, you can download many no.of ebooks for free, and it is the most used app by book lovers,
Go for bookchums app.