E-ink is the technology behind e-book readers such as the Opus. Some call it e-paper, but it’s essentially the same thing: a (relatively) revolutionary approach at computer-controlled displays. E-ink screens differ greatly from CRT or LCD screens, in several ways:

1. They are not backlit, therefore you need ambient light to see what’s on them
2. They do not require power to keep the image up
3. Their refresh rate is abysmal
4. They do not yet come in color, and they’re quite lame at showing gray too

So, you may wonder, why even consider buying something like this? That’s very simple: the things I mentioned above are the points of strength of these devices, not their weaknesses: it’s all about what you use these screens for. I am going to briefly go through those perveiced problems.

No backlight means no eye strain, period. You do indeed need ambient light for the screen to be readable, but then again you don’t read a book in the dark, do you?

The lack of backlight and the technology used also means that the battery life is extremely long: the batteries are only used momentarily when the screen is redrawn; in other words, the device is sleeping while you read a page, and only wakes up to turn the page. That’s why e-book readers’ battery life is commonly measured in thousands of pages, rather than in hours of operation.

E-ink screens, however, require a full refresh of the page (white → black → white → draw the text) to change the page, in order to avoid an effect called “ghosting,” which causes a hint of the previous page to vaguely persist. This problem, the lack of color, and the bare ability to go beyond a handful of shades of gray means that video won’t come to this technology before 2013 or so.

However, these devices are just great for reading standard books, such as novels. They are lightweight, long-lasting, clear and crisp, and the books themselves are usually very tiny in size: most of them barely reach one megabyte in size, and most devices have at least 1 GB of internal memory.

For more details about the technology itself, please read the page on Wikipedia. It comes with pretty pictures.