Ooh ironic.
Because there's currently a consultation about
extending the PLR to non-print books.
"1. Extend eligibility for Public Lending Right (PLR) to non-print books, in particular audiobooks and e-books;"
Anyway;
"How much would you be willing to pay just to read a book as opposed to own it? "
About 20p. Less if the format is inflexible for screen size.