It's disappointing that you call it overrated. I suggest that you obtain a copy on DVD and watch the interview with Rene La Loux. He describes the process of making this movie and his partnership with Roland Topor, the man who illustrated this movie. The history of this movie is very rich. When Soviet troops invaded Czechoslovakia in the sixties, where this movie was being made at the time, the production of it had to be halted for a while. Apparently, there are some missing scenes that never made it into the movie because of this.
Maybe you would enjoy reading "Oms by the Dozen" which was what this movie was adapted from.