Bell curve? 

"If there is any difference in "desirability", the bell curve of a normal distribution predicts that most experiences will involve average desirability, with roughly equal occurrences of excellence and gross inadequacy." I disagree: I think it would tend to follow a Pareto distribution with 20% of the books in a genre accounting for 80% of the worthiness of the genre as a whole. I think this is probably closer to what Sturgeon had in mind. Merlin