So, you can put together a fairly low end Linux machine (or a dedicated e-reader, I suppose) using an e-ink display, out of a raspberry pi or similar board. You need a secondary board to actually drive the display, as they take about 20 volts to activate (you can use a boost converter to get the needed voltages). The difficulty is in doing anything with a decent refresh rate, or greyscale.
Physically, the screens are basically hollow, filled with oil, and then differently colored differently charged particles (usually black and white at least). The idea is you apply voltage to a cell and it attracts the charged particles to the surface, where they stay even once the voltage is applied. Of course, how much voltage you apply, and how long you apply it determines how many particles attach and how long they stay. The most basic patterns are obvious enough that they’re known, but to do anything actually fancy with one of these displays, you need a fairly sophisticated pattern, the details of which are a closely guarded secret.
The e-ink displays you get, from Adafruit, or from one of integrated display companies, have an IC which takes care of the details for you, but they are all closed source. You can ask the display manufacturers for details, but only get them behind an NDA.
Still, you can get an e-ink panel screen replacement for a kindle or similar, rig up your own IC controller, and have black and white, with a bit of tweaking you can probably get broad-stroke grey. The fancy displays can hit 40 Hz, but I wouldn’t expect to get past about 6 Hz with a basic one.