Judging a Book By Its Cover

I recieved a question from a meebo guest who wanted to know where the phrase "don't judge a book by its cover" came from. I was able to discover in The Consise Oxford Dictionary of Proverbs that the popular phrase was first written in the book, Murder in the Glass Room (1946). The meaning, according to The New Dictionary of Cultural Literacy is "don't judge the value of a thing simply by its appearance."

Simpson, John. The Concise Oxford Dictionary of Proverbs. New York, 1992
Hirsch, E.D. The New Dictionary of Cultural Literacy. New York, 2002