Don't Judge a Book by its Cover (Idiom) 📚

Don't judge a book by its cover.

Do you know this idiom? It  means don't judge something  

or someone based on their outward appearance.

He may seem quiet, but don't judge a book by  its cover; he's an excellent public speaker.

The old building looks kind of  plain and boring on the outside,  

but don't judge a book by its cover.  It's absolutely stunning on the inside.