Until E-ink technology loses its laggy refresh rates, or a replacement tech starts being used, browsing through an ebook library is never going to be fun with a dedicated ereader. It's too slow, and much too cumbersome - true of all these devices including the PRS-650 and Amazon Kindle.
However, Sony has done its best with the technology's limitations and come up with a clean-looking and intuitive interface. From the home screen - always quickly accessible thanks to the front Home button - a third of the screen is taken up by the "continue reading" option. As this is by far the option you'll tap the most, this is a good design choice.
Underneath this are links to your books library, collections, notes, periodicals and tabs for applications and settings. Skipping into the books library - another very important piece of the UI puzzle - you can order your books in a handful of ways, and choose to see book covers or just the basic info. The slow screen response of E-ink stops the prettier graphical style from being practical though. You can't fit anywhere near as many book entries on-screen at once, and frustration soon sets in.
Switch to the more economical list option and the PRS-650 fares much better. It's still slow, but with a search function in tow you'll be able to find books within a few taps. With ebook readers like this, the less time you have to spend within the interface, the better. If you're willing to trade short-term frustration for longer-term ease of use, you can sort your books into collections too, accessible from the home screen.
In the spirit of convergence that devices like smartphones have forcibly encouraged on other kinds of tech, the Sony PRS-650 offers a few secondary functions. The ability to scrawl notes on your books is great, but the additional free-form doodling app is there for a bit of fun. The E-ink's refresh delay means lines you draw have to very noticeably catch up with the stylus, and it's all black and white. It's no replacement for the snazzy iPhone and iPad art apps available, but it's enjoyable for a quick scrawl.
Another support act feature of the PRS-650 is its music-playing abilities. Justifying the dual memory card slots, the reader can play AAC and MP3 files. The size and slow navigation of the device make it a poor replacement for a dedicated MP3 player though - even budget phones are more capable in this area. Playing music will also quickly eat into the claimed 2-week battery life - actual battery performance in real-world conditions is completely dependent on use (number of page turns), especially as there are no 3G or Wi-Fi connectivity options here to suck up juice.
The Sony Reader PRS-650 is on-par with the very best dedicated ereaders in terms of the reading experience it offers, but it's also one of the most expensive. The Kindle is the best part of a hundred pounds cheaper, and we don't think the smaller, more affordable PRS-350 is any worse an ereader.
The PRS-650 is a king among ereaders, but it also comes with a royal price tag. If you can stomach the extra expenditure though, its screen is top-notch, not dulled at all by the addition of touchscreen tech. Light, comfortable-to-hold and at least as tough as the competition, it's worth keeping as a constant literary companion.