Amazon's free Kindle app for iPhone may not provide as comfortable a reading experience as the full-size Kindle itself, but it offers many of the same features that make the Kindle such a popular e-book reader for just the price of the book. As with the Kindle, Kindle for iPhone lets you access e-books and samples, advancing the page with a simple swipe of your finger. Bookmarking pages, accessing the table of contents, and adjusting font size are equally easy, though even with an enlarged font, reading anything longer than a few pages can induce some eye strain.
There's also a fairly long list of caveats. Kindle for iPhone isn't conditioned to buying new e-books from Amazon.com--you'll have to buy through Amazon's Kindle store online via Safari on the iPhone or through your desktop browser. It also won't support periodicals and won't sync up sample e-books through the Whisper Sync feature (only those books you've already bought). The omission of an in-app e-book shop in the Kindle for iPhone app is the application's most significant limitation, an annoyance that could irk Kindle owners more than the significantly smaller screen size compared with Amazon's device.
For comic-book lovers, however, the iPhone app's full-color mode may atone for other sins, especially as long as the Kindle displays graphics in more than a dozen shades of gray.
Amazon's Kindle for iPhone could be a free hardware alternative to the Kindle device for casual readers who intend to read slimmer works, or those in short bursts. For voracious readers, the iPhone version is a nice companion app for when you want to pick up where you left off in a story without taking the Kindle out of your home, but not a replacement for the full-featured Kindle 2.