Violent Book

I bought my blind friend a cheese grater for his birthday. A week later, he told me it was the most violent book he ever read.

Explanation

Experiment

The humor comes from the misunderstanding of a blind person using a cheese grater as if it were a braille book. The grater's texture, when touched, could feel like a series of violent, raised bumps to someone who is blind and doesn't know what it is.