This opens up the Kindle Store for purchases from people who may not have a Kindle.

And, for people who have both a Kindle and an iPhone, Amazon’s WhisperSync feature keeps track of where you left off in a book as you switch between reading from your iPhone or your Kindle.

The Kindle for iPhone app is free and available for any iPhone or iPod Touch, with firmware 2.0 or higher.

From Amazon’s FAQ page for Kindle for iPhone:

The entire selection of books available for reading on Amazon Kindle can also be read on Kindle for iPhone. You can also download free book samples from the Kindle store and read the first chapter of a book before you decide to buy.

Periodicals such as newspapers, magazines, and blogs, and personal documents cannot be viewed on Kindle for iPhone.

Our members have already tested to see if these Kindle books can be synced to multiple iPhones, and it seems that they can. Kindleboards member Kristus42 was able to sync her Kindle Store content to two iPhones. I believe (but haven’t confirmed) that those multiple iPhones will count as among the six devices that your Kindle Store content can be synced to.

Once synced through the iPhone app, the iPhone appears under the “Manage Your Kindle” page on Amazon. And when you purchase books from Amazon’s Kindle Store site, you’ll see the iPhone listed under the “Send wirelessly to…” option.

Some more screenshots of the Kindle app:

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