Amazon has finally launched a Web-based version of its Kindle reader, allowing users to read their Kindle purchases on any device with a Web browser, without having to download special software. The Web-based reader, called Kindle Cloud Reader, sports both an online and offline mode and can even sync your last page read (among other things) across Kindle devices. But while Kindle Cloud Reader could be used by almost anyone, it's clear that the design was largely made for the iPad, allowing Amazon to sidestep Apple's in-app content constraints and even offer the iPad-friendly Kindle Store it couldn't implement in its native iOS app.

Since I'm an avid Kindle book reader on my iPad, I gave the new HTML5-based reader a spin on that platform to see how it differs from the native Kindle app. Upon logging in via read.amazon.com (which can be accessed from a browser, iPad or not), Amazon warns you that you'll have to authorize the Web app to expand its local database size up to 50MB so that you can download and store books for offline reading. If you're worried about the space, you don't have to store books offline—you can read them directly from the "cloud," so long as you have an Internet connection. However, as most Kindle users can attest, there are plenty of times in which you are likely to find yourself in the mood to read but without a connection—the train, the beach, during a power outage—so the offline feature is a definite plus.

Once you authorize Cloud Reader to take up more space on the device, you're presented with a screen listing every book you have purchased. Tap and hold any book and it will begin downloading for offline reading. You can toggle between Cloud and Downloaded books using tabs at the bottom of the screen.

The UI from within the book-reading interface is just slightly different from the native Kindle app(s). The default view keeps all of the controls hidden on the screen (same as on the iPad) until you tap the screen to bring them up. Things like book navigation, font size/page color, and bookmarks/highlights can be found across the top of the screen while your progress bar remains at the bottom.

Cloud Reader allows you to see the notes, highlights, and bookmarks that you've made from another device in any given book, but this is one area where Cloud Reader fails: you can't make new notes or highlights unless you go back to a native app or use a real Kindle.

Cloud Reader's main strength is its integrated Kindle store, which is one of the elements that makes Cloud Reader more suited for the iPad than, say, for the computer. The Cloud Reader's Kindle Store is not at all designed like Amazon's normal website—instead, UI elements are laid out in big, touchable areas and navigation is designed for the touchscreen user.

Accessing any of the typical book lists that you might get from the website is easy, and downloading new book purchases or samples is as easy as using the Kindle store on an actual Kindle device. And unlike the native Kindle app on the iPad, when you finish reading a sample, you have an easy-to-use way to buy the full version. (On the native iPad app, you must ditch the book sample altogether when you are finished, open up Safari, buy the book, send the book to your iPad, go back to the Kindle app, tell it to refresh, download the book, and then find your place again.)

Just for kicks, I gave the Cloud Reader a run around the block in Safari 5.1 under Mac OS X Lion as well (the Web app works under Safari and Chrome for now—Firefox isn't yet supported), and things functioned in pretty much the same way as on the iPad. You must re-download books that you downloaded in other instances of the Web app if you want to read them offline on different devices, of course, but don't worry about losing your spot; Cloud Reader can still sync your last read location across devices.

I have written in the past about Amazon's native desktop apps for Mac and Windows, and I don't consider reading books on the computer to be an activity that most people would do voluntarily, though Cloud Reader could work for people who want to sneak in a chapter or two during lunch at their office computers.

Aside from not being able to create notes and highlights, the cloud-based Web app has a few other drawbacks. If you subscribe to newspapers or magazines through the Kindle Store, you won't be able to read them via Cloud Reader. (Incidentally, the native iOS app only recently gained the ability read this content, so score one point for native apps.) The ability to search a book for keywords is also missing, and the built-in dictionary that some users have grown fond of is also nonexistent in Cloud Reader. And, although the Cloud Reader interface is quite smooth and responsive for what it is, the UI elements still react to touches and clicks perceptibly slower than the UI elements in a native app. (Feel free to insert an e-ink Kindle joke of your choice here, because nothing reacts slower than the Kindle hardware's own interface.)

Apart from the inclusion of the built-in Kindle Store, users have little reason to use Cloud Reader on a smartphone or a tablet over a native app. The store is the Web app's major highlight, and I can see people using Cloud Reader to buy content more than actually reading the content there. For reading, I still prefer either the native iPad app or the Kindle hardware itself, but the availability of the Web app does make it easy to read from anywhere. I don't believe Amazon will ditch its apps for iOS or Android, either—users like options, after all, and the experience is a bit more smooth—but Amazon has clearly seen the benefits of using the Web to get around app store rules.