How to sell a book

Endorsements by dead people. The far right does this all the time, claiming Martin Luther King would march with the pro-life forces or that he would back a lot of our present wars because he would realize the injustice we are fighting. Some even claim Karl Marx would embrace capitalism if he were around today and saw how well it's turned out.
Of course they are dead and can't speak for themselves. That's the beauty of finding a dead spokesperson. You can put your words in their mouth and they can't stop you.

See the picture below for an example