The screen works because of what it cannot do

The displays in the current reading devices cannot show video, cannot do colour, and take the better part of a second to change what is on them. Every one of those is why they work.

The mechanism is worth understanding because it explains the rest. Tiny capsules hold light and dark particles suspended in fluid, and a charge pulls one sort to the surface. Once they arrive they stay, with no power applied. The image persists because the particles are physically sitting there, not because anything is being held in place.

So the device draws power when the page changes and essentially none while you read it, which is why a charge lasts for weeks rather than hours. That is not an efficiency achievement. It is a consequence of the display being unable to do anything continuously.

The same applies to how it reads. There is no light coming out of it, so you are looking at reflected light exactly as you would with paper, which is why an hour with one does not produce the specific ache an hour with a monitor does. A screen that could illuminate itself would have to give that up.

Which is why I am wary of the improvements everyone is asking for.

Faster refresh, colour, and video are each individually reasonable requests, and pursued together they produce a poor liquid crystal display. The engineering to add them removes the properties that made the thing worth carrying, and you arrive at a device that does everything adequately and reading badly, which is a category that already exists and that nobody wanted for books.

The ugly full-page inversion when you turn over is the objection reviewers always lead with. It looks awful in a demonstration. It is also close to irrelevant in use, because you turn a page roughly every ninety seconds and the flash lasts a fraction of one. A defect that appears once per minute and a half is not the same class of problem as one you stare at.

I said in March that the interesting thing about these devices was the shop attached to them rather than the hardware, and I still think the business decides who wins. But the display is why the object is tolerable to hold for three hours, and that is not a small part of it.

Colour will arrive eventually and I hope it arrives as a separate product line rather than a replacement.