Also 300ppi is the sweet spot on an 8" display it's basically a near perfect paperback analogue and has a blue to orange backlight shift keyed to time of day.
It's basically my idea of a perfect ebook device.
As you can see it inverts and refreshes. The specs say a full update can take up to 4 seconds, but I've not yet seen one that slow.
I also got it as a gift to myself. If you would have asked me to spec out my ideal ebook reader, I would have ended up describing the One.
Some disadvantages: macOS doesn't have always recognise the device, it has 2.4 GHz WiFi only (put if off to save your battery). The Kobo's also have that screen refresh feature btw you can reduce its effectiveness if you're reading a lot.
Immediately after you bought it, check out the coating of the screen very carefully. I send one ONE back because it had a minor damage to the coating which caused bleeding. I found that distracting, YMMV. The 2 devices got it as well, but less severe and it depends on how you hold the device whether you notice it.
I looking at new Onyx Boox, which was just released: https://www.youtube.com/watch?v=1huyi7mgbzY . IMHO, it is much better than any Kobo on the market right now.
Kobo and Amazon don't contain *SD options but other e-readers do .
As insinuated, I find it is overrated. You can even run Calibre in Docker  to serve it over HTTP(S). And as you know, Kobo have a web browser. So you could put the books you're likely to read on your Kobo (8 GB is a lot) and serve the rest via that way. You could also serve the content over your phone via USB OTG.
If you're off the grid for a long time, I actually recommend something else instead: put your smartphone off, e-reader on, and keep a (at your option relatively, to <3 your battery) charged powerbank with you. Not necessarily for your smartphone, but for your e-reader!
 https://tweakers.net/categorie/804/e-readers/producten/ and select all options at the left at "Geheugenkaart Type (E-reader)"
Anyone aware of reasonably affordable greyscale E-ink displays at or larger than a piece of letter-paper?
There's an interesting thread from a year ago, but would love to know if prices have dropped/availability increased.
-would like a little better contrast on the screen, though it does seem roughly on par with kindles and the like with lighting off
-epub generally works well
-full size (ie, letter) pdfs do require cropping unless your vision is superior. The on-device crop is fine for text only pdfs but recommend using an external cropper for pdfs that have charts. Going this route has made it possible to read Reviews of Moder Physics on the reMarkable without the need to squint.
-it could use a 20% speed bump. Some of this might be achieved in future software updates.
You can, of course, use it for its other intended purposes - note taking and draw/sketching.
The product video does a great job at covering the trade-offs.
Unfortunately my device has only "black & white", no shades of gray at all, but I had a lot of fun working out how to drive it from a small MCU, without running out of RAM.
That's the same model/family of panel as the one showing 32 shades of gray in this article, and the author has done some other stuff with it:
Unfortunately my device has only "black & white", no shades of gray at all
That's because it's a module with its own controller for producing the display driving waveforms from the 1bpp data that you feed it --- but if you disassemble the module and figure out how to drive the display itself (it's probably not unlike the link above), you could get grayscale too. In addition, you could probably stream from network to display with almost no buffering, by clocking the data directly into the display as it's received over the network (although you'd have to clear each line before drawing it; unlikely to be very difficult, in any case.) Also, refresh as fast or slow as you want.
The reason I bring this up is because I recently had the idea of using small SPI flash memory chips to render the whoel.inage frame dynamicly. The SPI memory chips look like a neat way to easily do this by hooking one up to a small mcu and drawing the frame using the spi memory chop then dumping the whole frame from the memory chip to the screen. I hope to oder some small DIPs soon to experiment with and I thought it also might interest you as well.
Note though that making it paper-like requires just a reflective display. Transreflective is needed only when it also needs to function as an emmissive display or needs a backlight.
Reflective displays suffer from poor colors as the pixels get divided into RGB areas, which is contrasting with a color print because the printer can put any color ink anywhere. This is the reason E-Ink, and every other reflective display has found it hard to develop good color.
I have longed for a responsive color, paper-like display for long also.
Mirasol was one promising technology for that (latest demos could get excellent colors as it also did not need to subdivide pixel area into different colors, as colors were created using interference). However, there is no activity on mirasol for the last several years.
Note: I worked on mirasol for about seven years.
I recently got a Waveshare 4.2" e-paper for my Pi, and I've been playing around with a variety of dithering algorithms to get it to display images.
The Floyd-Steinberg algorithm seems to bring out the most detail if you look at the image from a distance, but ordered dithering (with the 8x8 Bayer matrix from Wikipedia) gave me a better "retro computer" look that I was aiming for.
I gave up my Kindle as soon as 5 inch displays were available. I thought the market would have made more progress by now.
I believe the reason is that there are a lot of patents/IP around the core technology, and it's owned by very few companies who essentially have a monopoly on the market. This also explains the secrecy surrounding the "low-level" details. As this article shows, you can definitely get more gray levels by driving the display directly.
From past examples, we will likely not see any real innovation in this space until these patents expire. It's especially disheartening to me since I'll probably be too old to get in on the action by then.
I hope societies reevaluate the role of patents in the advancement of human technology. From my perspective, patents do more harm then good. They encourage rent-seeking. They're impractical to use legally unless you have enough money. They hold back technology for a couple of generations each time a new breakthrough is discovered (as has happened with capacitive touch screens, 3D printers, and is happening now with e-ink displays).
To me, patents are achieving the opposite of their intended purpose.