Go to Barnes & Noble's website, they have 100,s of free classical books in .epub which is the standard format that all libraries use. You can download for free the Nook app.
I use them on my Ipad. I didn't care for the Kindle app as it doesn't allow me to expand on my Ipad, and it doesn't work with my library ebooks unless I go thru each one and convert which is a royal pain.