Zizek writes serious books. He's often known by the public for making jokes because that's what the public consumes: they don't read serious books.

Might you or someone else recommend which book or books might be a good introduction to Zizek? Thanks.

Zizek has made a joke once, that he has essentially written one book, but that about 60 times. If you want to seriously engage in his philosphical thought: "The Sublime Object of Ideology" is a good pick.