Books

My expectation was a crude/debauched way of interacting with books. “I’m gonna dogear the pages.”

Right, that's way too literal (pun not intended). Too superficial. Too easy.

A more nuanced interpretation of the joke than is apparent requires so much relatively heavy-lifting from the audience and/or for the audience to work backward from the decision that “the joke must be competent/fulfilling”.

Yep, there are several leaps of logic the audience must go through to arrive at the author's position. Hence it being much more satisfying when we get the joke. Moreover, there's also a transference of appreciation, and perhaps a bit of envy on the part of the audience that the "her" in this case has such a loving mate that we would all want the same.