Kindles:
Amazon has a larger catalog of modern books because
amazon has been in the e-book market longer than anyone other.They have 2,00,000 Kindle exclusive e-books with many from the famous authors who publish directly
via amazon.There are not many choices to buy e-books for the kindle from other stores or free book sites.The bought books are stored in the cloud.Just keep the local copies of the books.You can also lend a book to a friend once for 14 days.
Amazon also has kindle lending library which is currently available only to
amazon prime subscribers.Thus
via this service borrow books and read without buying.You can also read e-books loaned from the public libraries.Getting the loaded books onto the
device is simpler on kindle unlike the nook.The books can easily be downloaded wirelessly
via whisper sync service (an AT&T 3G powered connection).