[ulysses]

If it's a book that's only available DRM, I buy it on the Kindle. I'm not fond of buying DRMed books, but most are only available that way, and Amazon is the most likely to still be around in the future.

For non-DRM:

Tor Books are no longer DRMed.

Baen Books -- https://www.baen.com/ -- don't have DRM, and you can buy directly from the publisher, and manage your library on their site, and download as many times as you like. You can also often purchase eArc versions, and they have a monthly subscription bundle were you can read parts of the book as it comes out, and then you get the complete book when it's done.

If you're interested in translated Japanese light novels, there's J Novel Club -- https://j-novel.club/ -- for a monthly subscription, you can read book parts for free as they're being translated. Once they're fully translated, you can then purchase the final epub directly from their site.

Books are interesting in that they both are and aren't fungible. If, say, I want to read the next Martha Wells Murderbot book, or the next Julie McGalliard Rougarou book, I have to buy that particular book.

But if I'm just looking for another book to read, I always check Tor, Baen, and J Novel Club first.