Bibliomania

Emperor Mollusk conquered Earth peacefully, then retired. People keep coming to the planet to fuck with him, but he dispatches them all handily. Then one day, Mollusk runs up against someone who almost beats him. Mollusk, intrigued, goes after the villain.

This is one of those books that's supposed to be funny but didn't make me laugh. However, the story is fun enough to read that I still really liked it.