I want to start reading more, and I'd also like to start avoiding screens before I sleep, so I'd like to get an e-ink device that I can use for reading.

I've never owned or looked into ereaders before so I'm not entirely sure what the general capabilities are in this space, but heres a list of things that I consider important:

• Absolutely essential:
  • I need to be able to put my own files (epubs, pdfs, etc) on the device to read without being forced to go through some marketplace installed on the device (if anything I'd prefer there to not be a marketplace on the device at all, or a removable one, as I would never use it). Files don't need to be added remotely, as long as I can connect it to my (Linux) computer with a USB and mount the storage or pop out the SD/microSD to do that then that's sufficient.
  • I need to actually own the device, none of the techno-feudalist bullshit like what plagues the smartphone landscape. I want to be able to remove non-essential components (e.g. marketplace) and it'd be nice if I could also tinker and install third party software freely. If possible I'd prefer a device that's mostly or completely open and FOSS by design, but I'm aware that might be asking too much. As an alternative I would also be willing to hack the device to get it in an open, FOSS state if the process isn't too complicated and it's well documented, it'd be preferable if it was that way by design but as long as I can get there one way or another I'll be content.
• Would very much like to have:
  • In addition to regular books, it'd be nice if I could also read manga. These tend to be zip/rar files containing a series of images, so I'd assume support for reading things formatted in that way is probably less widespread if it exists at all on dedicated ereader devices.
  • Some kind of lighting so the device is usable in the dark. I don't know how this would compare to the blue light from screens (if anyone knows, please share) but I'll certainly want to use it for more than just before I sleep.
  • Some kind of system to add notes as I read might be nice, I was never good at studying and note taking in school so I don't know how much mileage I'd get out of it but in theory it'd definitely be a boon to organize information as I read or add notes to myself to look into things later or whatever.
• Would be nice to have, can live without:
  • The ability to load music onto the device and plug in headphones to listen to music while I read. Bluetooth for audio devices isn't really something I care about, but might be desireable in case I get bluetooth headphones in the future (unlikely). Unimportant if it has built in speakers or not, as long as I can plug in headphones.

I have tried Calibre & SumatraPDF, I was so excited for Calibre until it never worked properly on the one textbook I needed. For example, whenever I went to the next page it would stall on loading forever, and this is apparently a known issue that's [according to the posts I read from the owner] caused by a graphics driver that I'm not interested in delving into just to read an ebook.

The ebook itself is pretty large with a lot of mathematical equations and images, but nothing my computer should be stalling on. The issue with SumatraPDF is that it can't seem to render the mathematical equations properly, and I couldn't find any simple way to load them without having to do more work.

I usually just read ebooks on my phone using ReadEra, but I'm going to the beach in a few weeks and I'd like to buy a dedicated eReader so I don't burn through my phone charge (I usually stay on the beach from as close to sunup as I can manage to sundown). I'd like something that handles multiple file types, especially ePub, or at least doesn't require a proprietary file type or have RDM. I'd also like it to have a long-lasting battery (I frequently read for several hours at a time), and be sturdy/waterproof (because beach). I guess backlighting might be nice, togglable if possible, and if I could get on the internet to download files directly to the Reader that'd be nice too so I don't have to plan ahead. It doesn't need to be huge, in fact smaller is probably better. Price is definitely a factor, but I'm open to refurb if available for a higher-priced model.

Needs: Inexpensive, waterproof/sturdy, strong battery, ePub/open file types/no DRM

Wants: Backlighting, internet

I've done some comparison shopping but I'm waffling so I want other people's opinions. TIA!

eBooks and eBook readers feel a little stagnant at the moment. No significant increases in tech, the storefronts are stagnant and locked down with DRM, and it just isn't really an exciting field.

That said, I love my Kindle Paperwhite because it lets me get English books for cheaper (I live in Japan) and it lets me carry them around.

Do you use an eBook reader? Do you read eBooks on a standard tablet or phone? Or are you married to paper?

A while ago there was a post comparing e-books and hard copies. After chatting with a few people, I was convinced to spend the money on a Kindle to replace reading on my laptop.
It's an amazing difference and I'd recommend it to anyone who reads on a "normal" screen. My eyes don't get tired, night reading is more comfortable, I've got 40 books in my pocket, the screen really is glare free, and I've charged it once in a week and a half.
So if you read e-books, get a reader with the e-ink screen. It's worth it, and thanks to those who convinced me.