Since 1960s pop art the art world has been happy for artists to use the lowbrow to add zest and authenticity to their works. But middlebrow has resonances of the suburban bourgeousie who might see art as aspirational by association.

There's no difference between pulp fiction and highbrow fiction, one is as good as the other, the only difference is the aura they have, and that's determined by the people who read the stuff, not by the book itself. There's no such thing as 'the book itself.