alt Hacker NewsYou're just not describing what you want properly. Looks fine to me. Clearly you have something else in mind, so I think you're just not describing well. My tip would be to use actuall illustration language. Do you want a wide angle shot? What should depth of field be? Oil painting print? Ink illustration? What kind of printing style? Do you want a photo of the book or a pre-print proof? What kind of color scheme?
A professional artist wouldn't know what you want.
You didn't even specify an art style. 1970s sci-fi novel cover isn't a style. You'll find vastly different art styles from the 70s. If you're disappointed, it's because you're doing a shitty job describing what's in your head. If your prompt isn't at least a paragraph, you're going to just get random generic results.
The killer feature of LLMs is to be able to extrapolate what's really wanted from short descriptions.
Look again at Gemini's output, it looks like an actual book cover, it looks like an illustration that could be found on a book.
It takes on board corrections (albeit hilariously literaly).
Look at GPT image's output, it doesn't look anything like a book cover, and when prompted to say it got it wrong, just doubles down on what it was doing.