I love the aesthetics of hardback books, a beautiful Victorian-era library looks (and smells!) great but my own library is all ebooks. I don't have the space for over 2k physical books and as I get older and my eyesight worsens, the ability to adjust font size, line-height, borders, contrast etc becomes invaluable.
I won't buy from Amazon at all, ever. I prefer to buy DRM free but if its not possible to buy DRM free then I buy a paperback copy from a local indie bookstore if possible which I immediately donate to a library or hospital or prison or whatever and, ahem, 'source' a DRM-free version from elsewhere. I do it this way because DRM is cancer but I also want to support small and/or new authors so buying and passing on a print copy is good for everyone and having a DRM free copy is good for me.
As for subject matter, both fiction and non-fiction but more fiction than non. I like historical novels like the Aubrey/Maturin series, or the Shardlake series, Madeline Miller's greek retellings, Hilary Mantel's stuff, fantasy/sci-f- like Ursula K Leguinn, NK Jemisin, Margaret Attwood, Robin Hobb, Lois McMaster Bujold, Susannah Clarke, Adrian Tchaikovsky. Horror/Thrillers by writers like Peter Straub, Catriona Ward, Shirley Jackson. Non-fiction books tend to be popular science that are 'popular' enough I can grasp what they're on about but 'science' enough they're not just dumbed down crap.