Choosing the right e-reader definitely starts with screen size, because a reader that's great at home may be annoying to carry around.
Six-inch readers such as the Kobo Clara BW and basic Kindle are compact, light. Pretty close to the feel of a paperback.
Seven-inch readers like the Kindle Paperwhite and Kobo Libra Color give ya more screen space without being too bulky.
Eight-inch models are comfortable if you use larger fonts, while 10.3-inch readers make much more sense for PDFs, textbooks, magazines, and comics. I have two of these, and I still think they suck for PDFs and textbooks though. I mostly just use them for novel reading in bed.
And some good tiny, phone-sized E Ink readers now like Xteink and Boox. For ordinary novels, though, I think the 6-to-7-inch range remains the sweet spot for most people.
Next question is where your books come from. Kindle's probably the easiest choice for people who buy almost everything from Amazon and don't want to do much beyond buy, read, and delete. The current Kindle Paperwhite has a 7-inch 300-ppi screen, front lighting, waterproofing, USB-C, and great battery life, but just know that Amazon keeps fairly tight control over its ecosystem.
You can still send EPUB files through 'Send to Kindle' or transfer compatible files from a computer. Some people worry about relying too heavily on features Amazon controls, since those features can always change. But if you're mostly buying trashy romance novels, reading them in three days, then deleting and on to the next one, that may not matter much to you.
My wife is like that. She has a newer kindle, buys her ebooks on amazon, reads them, deletes them, then goes to buy another. She reads Amish Romance and Alphabet murder mysteries, and sometimes some vampire romance books. She gives zero fucks about what DRM is or sideloading or anything. And she never re-reads books. So if this is you, go for it.
Kobo is a better fit for people with their own DRM-free EPUB libraries because Kobo reads EPUB directly and works great with Calibre.
PocketBook also good for sideloading and supports a large number of ebook formats.
If you enjoy modifying your hardware, Kobo is probably the best mainstream choice. KOReader supports most Kobo models, including some very old ones, and normally does not require replacing Kobo's original software.
You can keep the normal Kobo interface and launch KOReader when you want it. PocketBook is also unusually friendly to alternative reading software. Kindle is more restrictive. Some older Kindles can be jailbroken and modified, but whether you can do it depends heavily on the exact model and firmware version.
There are also inexpensive-ish smaller readers that appeal to tinkerers. The Xteink X4 can be flashed with alternative open-source software such as CrossPoint, which is my personal fav.
Used e-readers deserve serious consideration. E-Ink tech is pretty sold, so lots of older readers still work fine. I have Kindles and Sony e-readers that are approaching 20 years old and are still perfectly usable.
One of the best examples is the Kindle 3, better known as the Kindle Keyboard, released in 2010. Working examples can often be found for around $40 to $60. 6-inch E Ink screen, physical page buttons, 4 GB of storage, and a full keyboard. Connect it to a computer, copy your books over, and you're good to go. Replacement batteries are also pretty common, and there are plenty of YouTube tutorials showing how to replace them. It's very easy. I've done it plenty of times.
There are several other good used choices. The Kindle Paperwhite 3 is one of my favorites because it combines a sharp 300-ppi screen with built-in lighting and can often be found for around $60 to $85.
On the Kobo side, the Clara HD remains a great little six-inch reader with warm lighting, while the Libra H2O and Libra 2 are great choices if you want a larger screen and physical page buttons.
Older Kobo models are nice because they still work well with Calibre, sideloading, and KOReader. With any used reader, I'd worry less about its age and more about the battery, screen condition, and USB port. A ten-year-old e-reader with a healthy battery can still do its main job just as well as it did when it was new.
So my personal recommendations are a mix of new, used, and highly portable readers:
Kobo Clara BW is a great straightforward black-and-white option.
Kobo Libra Colour is a strong premium all-around reader.
Kindle Paperwhite makes sense for heavy Amazon users.
BOOX Go 7 is best for someone who wants Android and maximum software freedom.
For used readers, I'd look for a Kindle Keyboard around $50, a Kindle Paperwhite 3 around $40 to $60, or a reasonably priced older Kobo.
My personal favorite e-reader right now is my Xteink X4,(regular X4, not the X4 Pro). Cost me $55 after a discount, gets great battery life, can be flashed with CrossPoint, and is small enough that I can take it practically anywhere.
One thing I use with all of my e-readers is Calibre. A free, open-source ebook management program that lets you organize your library, edit metadata and covers, convert books between formats, and transfer them to a huge range of e-readers by cable or wirelessly.
Calibre supports almost every major e-reader and can automatically convert a book into a format that works with your device. If you own several different brands of readers, it makes managing everything much easier: https://calibre-ebook.com/
As always YMMV, and you may prefer built in lights and extras. Just know the more extras you have, the higher the price. It's also good to do quick research and read reviews of whatever reader you're gonna get.
