Caligula effect; forbidden fruit effect
A psychological phenomenon where restricting or forbidding something increases desire for it. The term comes from the title of the 1979 film "Caligula", which gained notoriety and interest due to censorship and controversy.
Because of the Caligula effect, a banned book becomes even more desirable to read.
It is said that this movie's success is an example of the Caligula effect.