The Kindle and Sony Reader gadgets have new competition: the iPhone, iPod Touch and BlackBerry smartphone, among others. That’s because ginormous bookseller Barnes & Noble has announced its own electronic book store.

The Barnes & Noble eBookstore is being touted by the company as the world’s largest electronic bookstore, with more than 700,000 titles available now, and more than a million within a year. In addition, about half a million public domain books are available for free from Google.

All that is good, but the better news is the number of available platforms you can use to read your tomes. The eBookstore is available for the three aforementioned devices, as well as other smartphones, and Mac and PC laptops and desktops. In fact, the company says that its application for the iPhone and Touch is the most popular book-related download in Apple’s App Store.

This should make things interesting for the Amazons and Sonys of the world. Having multiple ways to read books is a good thing; on the other hand, the uniqueness of the specialized readers is that they more closely simulate the experience of holding a book in your hand, which smartphones can’t match — at least not yet. Still, I know a new app I’m going to be downloading today for my iPhone…