On Bullshit by Harry G. Frankfurt

This teeny-tiny hardcovered book (4" x 6", 67 pages) was written by a Princeton professor of philosophy. It is serious in tone as the professor tries to define his subject. However, about two-thirds of the way through, I was gobsmacked by the thought that "This is bullshit on bullshit." Then the author pulls it together with a rather reasonable ending and the reader is left wondering if it is parody or not.