It’s been proven to be about as true as gravity.
I agree. It is one of the few books that one can read over and over.
I spent 43 years in a large organization and saw every aspect of the Peter Principal in play.
I followed the Peter Parry, whereby an individual realizes he has reached his level of complete competence and utilizes clever ploys to guarantee that he will NOT be promoted.
Bottom Line: The nay-sayers MUST READ THIS BOOK !
You must have read the sequel “The Peter Prescription”.
Many good tactics in there to remain at one’s level of competence.