The operating system that drives the Kindle Paperwhite is quite a departure from previous Kindle devices. Like the overall physical design of the Paperwhite hardware, it takes various cues from the Kindle Fire HD.
Since there are no physical buttons, navigation primarily consists of screen swipes and other gestures. Tapping on the right of the display will turn the page forward, while tapping the left most portion of the screen will turn back the page.
Topping the upper portion of the screen is the Kindle toolbar, which on a purely visual level, is much like the upper portion of a web browser's window or many desktop application interfaces.
When inside a book, you have four basic tools. First is Fonts, where you can choose the size of the type, and as well typeface, from six options in total. Line spacing and margins can also be adjusted. It's worth noting that the menu appears like a pop up window that you'd find in Windows or OS X, right down to the X in upper corner, which can be used to dismiss the tool and get back to your book.
Next is the Go To menu, which allows you to navigate various portions of a book and jump between sections in a quick manner, depending on how the book itself is laid out.
X-Ray lets you explore the "bones" of a book, as Amazon puts it. It's essentially a more robust, in-depth version of Go To, it goes beyond the book itself. Selecting X-Ray provides a list of all the noteworthy characters, places, phrases, even themes contained on a single page, in a chapter, or the book as a whole.
Choosing a particular phrase or word provides additional background information. In the case of characters or locations in non-fiction, Wikipedia will be referenced. If not, curated information from that particular book's Amazon-selected expert handles the embellishment.
This feature does not use the web for reference; instead it refers to an additional file that comes with X-Ray-supported titles. As a result, when pulling up info, it's instantaneous, and no internet connection is required. That means you don't need a constant WiFi signal to use this feature, it just needs to be am X-Ray compatible title.
At this point not a whole lot of books support this new feature, but hopefully the numbers will grow over time. It's a great tool for keeping track of extended casts of characters.
Finally there's the Share button, which allows you to share portions of a book with other users. To select a word, simply hold your finger on it. Immediately, a pop will appear, asking if you'd like to highlight it. Here one can also find the definition of the word, provided that a dictionary is loaded on the device (there are countless free dictionaries provided by Amazon, but none are pre-installed; they must be downloaded first).
When it comes to adding a personal message, the on-screen keyboard will appear. It is here, along with the navigating the new operating system as a whole, in which Kindle veterans will note how much snappier everything moves along. While there is still a delay between action and result, it's nowhere near as slow and pokey as with the first generation of Kindle devices.
Though many who are used to more modern mobile operating systems, like iOS 6 or Android 4.1, might find it a bit of a culture shock. A few things feel like they should be faster, more immediate. However, given how little you'll interact with the operating system, compared to an iPhone or Android tablet, this is a minor inconvenience.
The only issue is when it comes to typing; there is a tendency for the Paperwhite to miss a text input, which will require you to go back and try again. Simply typing a tiny bit slower will solve the problem. Basically, if you don't type like you're hurriedly texting a friend, but simply making a notation, there won't be problem.