Bill Maher's New Rule For Bristol Palin (VIDEO)

Writing a book is hard. But having someone write it for you is even harder. You have to tell them the whole story, read what they've written, make sure they got it right, and then you have to go on tour pretending that you're the one who actually wrote it. That takes a lot of determination and commitment.

Of course, you could also just invite your ghost writer to promote the book with you and let the chips fall where they may. But Bill Maher is not on board with that idea. In this exclusive look at Friday's show, Maher sounds off on why it's better to maintain the illusion.

Take heed, Bristol. We may not have believed you actually wrote a book, but we were willing to fake it right along with you. You have to keep up your end of the deal, though.

"Real Time" airs Fridays at 10:00 p.m. on HBO.