You can publish the book in print and simultaneously in electronic format and then just give a link to a private cloud storage, where there is already an index without the possibility of downloading or copying the book. For example I like the book The Double Helix after reading the summary with https://freebooksummary.com/category/the-double-helix, it tells about the discovery of dna. If it were in electronic form I could often come back to it and find the pieces I need about the researchers without reading the entire volume. And about the fact that it is expensive there are free repositories with link access, you can duplicate the book there and give a link when you buy it.
