You use this proverb to say that you can’t tell what something/someone is really like just by looking at it. It might be different from what it looks. If someone says, “You can’t judge a book by its cover,” he/she advises you not to judge someone or something only by its appearance. People also say, “You can’t tell a book by its cover.” For example: “I know you want to think he’s honest and trust him, but be careful. You can’t tell a book by its cover.”
Magyarul: Ne ítélj első látásra!
