Hard scifi by Greg Egan is a trip and you'll never be the same afterwards. Permutation City and Diaspora are my favorites.
For more modern take, Children of Time is beautifully narrated and I could listen to it all day for years and never get tired of the narrator.
For a universe that keeps on going with problem solving Vorkosigan Saga is very feel good and I think in line with a book like the Martian albeit a bit less hard though solid on its approach to deduction and wit.
As a dm I do this too for npcs and sometimes for pcs if they have a specific concept. Otherwise it takes hours of searching and you always have to settle, nothing is quite right. I don't see an issue with it, no hobby dm can spend money on an artist creating every npc and it's not feasible to expect it. This way I get high quality art if I'm willing to put the effort in to sorting and correcting images through repainting. Especially since I run a campaign set in feudal Japan. Orcs and kobolds in japanese traditional garb is not very common! Ai even let me run an encounter of a fashion show by providing the players a bank of images to curate a collection from and compete with other collections I made using ai.
I still spend money on patreon for monster tokens and maps and I doubt that would change even if ai could make good ones. I pay for their creativity and concepts not just the art.