Unfortunately, I don’t have that option; not sure if it changed with the newest update. When clicking on the 3 dots on a book title, the closest option is to remove download, which would still leave the book cover, or permanently delete, which would remove the book from the cloud.
@my3girls solution did exactly what I needed! I did permanently delete the ones I knew I would never read, but kept a couple that there was a slim chance I might read, but don’t have to see the covers on my home screen!