can’t judge a book by its cover

C

can’t (or don’t) judge a book by its cover

Meaning

• outward appearance cannot be an indicator of someone or something’s value or worth
• you cannot know what someone or something is like just by looking the person or thing’s appearance
• the quality or character of  someone or something cannot be judged just by looking at them
• an opinion of someone or something cannot be formed solely by seeing what’s on the surface

Example Sentences

1. The candidate did not look very intelligent, but you can’t judge a book by its cover.
2. The hotel looked attractive from outside, but the rooms were damp and not well maintained. You can’t judge a book by its cover!
3. Do not form opinions of a persons character by looking at his appearance. You can’t judge a book by its cover.
4. At first we did not want to go into the restaurant as it looked small and cramped; but the food was delicious – we realized that you can’t judge a book by its cover.
5. The car was small and looked unsuited for a long trip, but packed a lot of power and was very solid. You can’t judge a book by its cover.
6. That man may look very small and insignificant, but don’t judge a book by its cover – he’s a very powerful man in his circle.

Origin

In George Eliot’s The Mill on the Floss (1860), Mr Tulliver uses the phrase in discussing Daniel Defoe’s The History of the Devil.

‘The History of the Devil’ by Daniel Defoe; not quite the right book for a little girl,” said Mr. Riley, “How came it among your books, Tulliver?”
Maggie looked hurt and discouraged, while her father said, “Why, it’s one o’ the books I bought at Partridge’s sale. They was all bound alike, it’s a good binding, you see, and I thought they’d be all good books. There’s Jeremy Taylor’s ‘Holy Living and Dying’ among ’em ; I read in it often of a Sunday.” (Mr. Tulliver felt somehow a familiarity with that great writer because his name was Jeremy); “and there ‘s a lot more of ’em, sermons mostly, I think ; but they ‘ve all got the same covers, and I thought they were all o’ one sample, as you may say. But it seems one mustn’t judge by th’ outside. This is a puzzlin’ world.

The preceding version was then publicised by the 1946 murder mystery novel by Edwin Rolfe [de] and Lester Fuller, Murder in the Glass Room, in the form of “You can never tell a book by its cover.”