An indepentant ebook store
Just to maybe broaden your reading options a bit... this site https://www.fifobooks.com/ has ebooks written by indie authors. Not the big names, but self publishing and small publishers.
The books are DRM free and iPad/iBooks friendly. Prices are pretty good as well. When you buy a book, just download it to your computer. Then import the file into iTunes and it will show up in your books. If there is an option, be sure to get the ePub format....
Not for everyone, but another option..... and I like options :)