Get any Kobo and immediately install koreader:

http://koreader.rocks/

This is the best answer. I'll also suggest Calibre for file management.

I'm the same as you wrt expecting my e-reader to work offline, and got a Pocketbook Verse (~$115 on Amazon in the US) that I've been happy with. It supports Wifi but I've never needed to connect it to the Internet and it works totally fine. No accounts, and has an SD card slot so you can just dump all your books on a microsd, slot it in, and the reader will automatically index them and make them available in the default reader app. The web browser and "store" (not sure if it's an app store or a book store - never tried to use it) don't work offline, obviously.

I was about to recommend it to you with no shortcomings, but I just turned it on to check the model, and it greeted me with a popup letting me know that "Pocketbook works better on WiFi! Connect to WiFi to make the most of your device!". I've never seen that popup before in the months I've been using this thing, it was easily dismissable, and everything that you'd expect to work still works fine offline, but that did just sour me on its offline story a little.

Another vote for the Pocketbook (~€100 on online stores in Europe). As the parent above, I never connected it to the internet, not once. I use a USB cable to add new books. The Pocketbook is also recommended by Mozilla's Privacy Not Included list as the most privacy-friendly e-reader. I wrote a blog post about my Kindle → Kobo → Pocketbook experience: https://suffix.be/blog/search-perfect-ereader/

Thank you, I'll have a look at those, they seem better priced than the kobos too.

You can bypass Kobo registration by connecting it to a PC over USB and modifying the SQLite database on it.

Then you can use calibre to transfer ebooks to it.

I second this, Kobo is still easy to hack on and make good products. It does seem that they are pushing their new colour models and are 'Out of Stock' for many months on their cheapest model B&W model (the Nio).

I got the color one. Unless you REALLY need color, get the black&white one. The color technology requires going through filters, which reduces brightness and resolution a LOT.

I use kindle. Have wifi turned off, and just load the books over usb using calibre. When you buy the kindle books off of amazon, you can download them to your computer to then put them on the device, theres some DRM in there so only your devices will be able to read them.

You still need to register the kindle with your account, but after that, it can be an offline device

I am using Tolino readers completely offline. They show up as mass storage device, and cloud/shop/library connectivity is completely optional. I do connect them to wifi periodically for software updates, but that doesn't require any registration either.

I’m curious - what is the motivation for the “offline only” requirement? Where are the boundaries of what’s negotiable and what’s not? For example, is it ok if it can connect to the internet but doesn’t? Or is the existence of a TCP/IP stack or a wifi chip a dealbreaker? How about a 1 time software update on first boot? etc

It's fine that it CAN be used online.

It's a deal breaker for me if it it (even once) HAVE to be.

It's a deal breaker if it artificially limits functionality, for example, by only providing dictionary functionality via an online service, or a substantially worse offline alternative.

It's a deal breaker if it continually nags me to connect it. It can ask once or twice, or show a "disconnected" status icon just fine, but it shouldn't nag, it shouldn't pop up dialogs reminding me to connect or otherwise hinder me in using it for it's primary purpose.

It should be able to fulfill it's primary purpose (for an ebook reader: provide a comfortable and convenient reading experience) should be 100% available without me needing to ever put it online.

Forced software update on first boot is an absolute deal-breaker. Any kind of enforced scheduled update is a deal breaker.

As for the motivation: Control, predictability, reliablity.

Control: I want to buy a product that is in some known state, and then myself decide if I want to risk an update (for an ebook reader that's so badly done that it needs a software update to do the one thing it's supposed to do, that's a nogo).

Predictability: I generally don't want my stuff to change, I like my stuff for what it is, and if I want it to change, I want it to be MY decision, and not something forced upon me.

Reliability: I prefer the bugs I know, and can work around today, to the bugs that I don't know, and must learn to work around tomorrow.

Reliability is more than simply uptime for me, it's also that I'm able to rely on exact behaviors, I want to be able to rely on the thing to behave the same way tomorrow and in 10 years, as it does today. I want to be able to learn how it works, and not have to throw away what I know at random times for no reason.

I have a Kobo Libre 2 which I use purely offline. To transfer files, I drag and drop via a USB cable. It's a comfortable size, has good typeface options, and has two physical buttons for turning the pages. It's a pretty simple setup that I would recommend.

Kindle Scribe works offline (i have the wifi turned off all the time). I think you can upload books and the like offline as well using an App (i usually send books over email, though)

I am sorry but this post is a trigger for me. Kindle scribe is slow, laggy, and 100% unreliable. I paid over $400. My files and books disappear randomly. I talked to Amazon customer service and they had me sign out and back in. Everything was completely reset and the problem was not solved. Amazon needs to hire some product people who use the stuff they sell. I 100% believe that in best case, Amazon's Kindle business unit is led by managers who does not use their products. Worst case they hate people who want to read. It is really sad. Kindle used to be good product. In last 3-4 years it has nose dived in quality.

i use FBReader on my phone. I realized that I only find time to read suddenly, and I never plan, so my e-reader would lie idle, and my phone is always with me.

Pretty sure a HN comment lead me to buying a Kobo Clara, strongly recommend!

Take the book printed out. It's healthy, distraction free

I do enjoy reading on dead wood as well, but for my bedtime routine, an ebook reader with an extremely weak backlight or frontlight really is the way for me, because it's slightly more convenient for me not to have to deal with room light and when I close the ebook reader, it will remember where I was. With a bookmark I often forget to put it back in, or I leave the book open and it falls to the floor causing me to forget... Also, English is my second language, so I find it very useful to be able to quickly look up the meaning of words (something I really valued about my now broken Kobo was its dictionary).

I would like to point out your comment comes across as very stack-overflowy.. It's the class of comment that does not answer the question, but instead suggest a solution to a different set of problems. I don't think my OP could reasonably be interpreted of me asking about other ways of reading books :) I'm guilty of this as well, but it's not very helpful and it tends to come across as snarky rather than clever.

Depends on the type of book. Although it might work for textbooks or something you would read at a desk, it wouldn't have the convenience you get from a paperback or an e-reader (eg, you can easily take out a ereader on the train, pack it for a trip, etc.)

Loving my Kobo Clara 2E!