They’ve been called the next revolution in books - electronic books or eBook Readers. Amazon’s Kindle is arguably the most popular although there are other models by other manufacturers.
eBook Readers don’t use TFT technology. Staring at a TFT screen close up for long periods can cause eye strain - and TFTs eat batteries and any laptop owner knows.
Instead, they use a technology called e-ink which consists of black and white particles that stick to the screen using positive and negative charges. The screens aren’t backlit and the result is more paper-like than a TFT screen. The current resolution for most units is 600 x 800 which is ideal for reading books.
Power To The Image
Power is only required to change an image, not maintain it, so battery life can be measured in days rather than hours. If you switch off the wireless connect feature, the battery could last for well over a week.
Although e-ink is currently only black and white, most eReaders support eight levels of grey. Some Amazon Kindle models support 16 shades. One thing you’ll notice about eReaders is that ‘turning the page’ can take a second or so. Early models took over a second. It’s no big deal but it looks strange initially. Also, the page turns black before the print appears.
Navigation is by way of controls on the unit. Amazon’s Kindle includes a keyboard which you can use to annotate parts of the text - ideal if you’re prepping for exams - or just a compulsive margin-writer!
Book Formats
Different eReaders support different eBook formats. The most common eBook format is EPUB (which is rapidly becoming the text equivalent of mp3) although the Kindle currently 
does not support this. Amazon prefers its own custom AWZ format which only the Kindle reads and it allows Amazon to protect books with DRM. If you change eReaders in the future you may not be able to take those books with you.
Apart from EPUB, it does read a few other eBook formats (Project Gutenberg is converting its library to Kindle format, too) and it has a text-to-speech features if you need a bed-time story.
Amazon has far and away the largest number of titles to choose from. The Kindle can connect directly to the Amazon store via 3G. As this is not WiFi, it means you can connect anywhere there’s a mobile phone signal. You don’t have to rely on WiFi hotspots and you don’t have to download books to your PC and then transfer them to the Kindle.
There is, however, currently a bit of a war going on with book publishers and eBooks are often as dear and, in some cases, more expensive than, their paper equivalent. Go figure!
The relatively new e-ink technology, which will doubtless improve over time, got eReaders off to a crawling start. They were expensive and slow to catch on. However, eReaders are growing rapidly in popularity and the Kindle is one of Amazon’s best sellers.
You can’t fully appreciate the wonder of these machines by looking at photos. You need to hold one, read a little and turn the pages. You’ll never look at a book in the same way again.