The phrase 'Don't Judge a Book by its Cover' means you should not decide upon something based just on outward appearances.
Example of Use: "I’m glad I didn’t judge a book by its cover, or I never would have married him!"
Interesting fact about Don't Judge a Book by its Cover
The origin of the idiom 'don’t judge a book by its cover' is fairly recent. The phrase is attributed to a 1944 edition of the African journal American Speech: “You can’t judge a book by its binding.” It was popularized even more when it appeared in the 1946 murder mystery Murder in the Glass Room by Lester Fuller and Edwin Rolfe: “You can never tell a book by its cover.”
