Book cover: should fit your genre or category, appeal to target readership

• Self-publishing: Conduct competitive title research, look at bestsellers in your category or subgenre.
• Traditional publishing: Share your knowledge of the reader with your publisher; share covers with the right positioning.
• Case study: https://insights.bookbub.com/ways-book-cover-hurt-sales-fix/
• More advice: https://createifwriting.com/how-to-choose-the-right-book-cover/
• And: https://createifwriting.com/four-ways-to-screw-up-your-book-cover/