I contribute to Standard Ebooks that takes PD text (primarily from Gutenberg but also elsewhere) and reformats it with good typography and consistent styling, before re-releasing it as public domain again. We’re coming up to 300 titles now, any problems you find can be fixed with a pull request on github if you want: https://standardebooks.org/

Baen Books

https://www.baen.com/

They have always been very customer friendly. They have a "free library" section, too. (Often has such things as the first book in a series.)

J Novel Club

https://j-novel.club/top

Translated Japanese light novels. There's a membership that lets you read along as they translate, but if you purchase the ebook when they're done, it's DRM free.

And of course http://www.gutenberg.org/

It's not the same as buying DRM free, but stripping DRM from most eBook formats is pretty trivial these days, afaik. Unless something has changed in the last few years since I last bought a kindle edition of a book (which I stripped of DRM so something like this couldn't happen).

It’s not trivial for Kindle anymore. I did it recently on a Mac, and it took a fair bit of work, was complicated and confusing, and required finding an old version of the Kindle reader program and somehow preventing it from checking in with Amazon’s servers. My brother in law recently tried and failed after having done it in the past.

It's still trivial AFAIK (I last did it one or two years ago) if you have an old kindle device, and can therefore convince Amazon to send you the poorly encrypted files meant for old kindles. I use a "Kindle Keyboard" e.g. the 3rd gen. Amazon has stopped selling new-old-stock, but it seems you can still find them on ebay for somewhere between $20-50.

Incidentally this model of Kindle also comes with text-to-speach, which is a really nice feature which I believe is missing from all newer models (removed to avoid cannibalizing audio book sales.)

Keep in mind that by buying DRMed books you give companies an incentive to produce them. If you're opposed to DRM, it may be better to pirate instead. Especially if you live in a jurisdiction in which removing DRM is illegal so you're breaking the law anyway.

tor is a scifi/fantasy+adjacent publisher that famously offers drm-free ebooks

https://www.tor.com/

If you live in the US and have a library card, try Overdrive. You can check out a huge catalog of eBooks for essentially free (since it’s paid via your local library).

Overdrive ebooks are DRMed (or at least the majority of them are).

Overdrive primarily uses Adobe's DRM system. You can "liberate" the titles with the use of the DeDRM toolset or get the resources directly off their "libby" platform, which simply requires reassembling the assets into an EPUB

I know you can break it, but this is in response to someone asking a question about how to buy DRM-free ebooks.

Looks like some people are forgetting the first rule of Fight Club.

It’s not too hard to break this DRM. My library lets me ‘borrow’ ebooks and sometimes they are due back and I haven’t finished them.

It’s so ridiculous.

Don’t forget https://www.humblebundle.com/ for frequent book bundles.

Packt, Manning, O'Reilly

I buy mostly technical e-books.