The very top of the Kindle Paperwhite toolbar has options that provide consistent controls, in or out of a book. First there's the Home button, which provides an immediate exit from a book to the launch page. Upon turning the Kindle Paperwhite on, this is also where everyone will start.
At the upper left of the launch page are two sections, Cloud and Device. Cloud is your entire Amazon library. As noted, in addition to whatever books you might already own, you'll find a variety of dictionaries for download.
To navigate this portion of the Paperwhite, simple taps will not do. Instead, you'll swipe back and forth, like on an iOS or Android device. Upon getting all the way to the beginning of a sub-section, the Back button comes into play. It's a bit jarring, this little navigation inconsistency (simply tapping the Home button will suffice in most occasions), but it's nothing earth-shattering, and we got used to it quickly.
Next to the Back button is a light bulb icon that allows you to adjust the screen's brightness. As noted previously, there are 24 different levels, which should insure a comfortable degree of illumination in almost any circumstance. The only quibble here, and it's a minor one, is how there's no immediate on/off, or toggle options. But again, the Paperwhite's OS is so snappy that the omission is not a true issue. Dragging your finger down your slider works well enough.
Then we have the Kindle Store button. Here you can browse books, newspapers, magazines, and more. It's easy to make purchases directly from within the device. The layout is similar to the experience of shopping with Amazon on the web. Any purchased material shows up in the Device immediately.
The Kindle Store is the device's killer app, and is even more impressive than the Paperwhite's advanced display. There's simply more reading material here than on any competitor's marketplace.
Right next to the Store button is the universal search function. When inside a book, it can be used to search for specific words and terms, though outside, in the main screen, it can search across all the items in your library, provided that they are installed on your device (meaning items in the cloud but not synced to the device will not appear). Inside the store, it can be used to look for all things within Amazon's ecosystem.
Finally we have more advanced options, including settings and sync related options. One can find special offers in the Kindle Store, as well as a means to organize one's library, by placing them in Collections. Though the most interesting item of them all is the Experimental Browser.
Experimental is putting it mildly. It's designed to serve up popular portals, often mobile versions, as well as full pages properly, but it's very tough to navigate, and is the only time in which the Paperwhite feels as if its over extending itself. It's really not worth the bother.