Maggie Cramer 
August 29, 2020 
Common Phrases You’ve no doubt heard this very common saying before, perhaps from your parents when you were younger, as it conveys an important lesson—one not actually, or at least not exclusively, about books, as you might guess. Read on to discover the meaning of the idiomatic expression don’t judge a book by its cover.
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The phrase don’t judge a book by its cover means that you shouldn’t make a judgement about someone or something—be it a book or otherwise—based solely on their or its outward appearance. After all, a cover of a book may be boring, just plain without an image or illustration, yet its pages be filled with highly entertaining characters and stories. If you were to only consider its cover and decide to pass it by, based on first impressions without a deeper look, you’d miss out on a great read. Just as a person may look absolutely beautiful or handsome on the surface but be uncaring and unkind. If you were to form an opinion of them just on their visible qualities, you’d be wrong about their true character. In other words, you shouldn’t make a superficial judgement about someone or something, because it’s impossible to know a person or thing’s value or true nature based on appearances.
Here are a few example sentences using the expression don’t judge a book by its cover:
You’ll also often hear or see this expression as you can’t judge a book by its cover. Other variations include you shouldn’t judge a book by its cover and never judge a book by its cover.
The saying’s origins aren’t entirely clear. It’s thought to have originated with George Eliot’s 1860 novel The Mill on the Floss. In it, the characters Mr. Riley and Mr. Tulliver are discussing a book Mr. Tulliver’s daughter, Maggie, is reading called The History of the Devil. Mr. Riley is surprised Mr. Tulliver is letting her read it, but Mr. Tulliver explains he only bought it for the cover and didn’t know what it was about. Mr. Tulliver says:
“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.”
As you can see, it’s not the phrase exactly, although the sentiment is very much the same. Despite this, George Eliot is often attributed as saying don’t judge a book by its cover.
The phrase appears as we know and use it today just a little while later, in 1867, in an article in the newspaper Piqua Democrat:
“Don’t judge a book by its cover, see a man by his cloth, as there is often a good deal of solid worth and superior skill underneath a jacket and yaller pants.”
Clearly, the phrase started catching on around that time. The 1940s murder-mystery Murder in the Glass Room by Edwin Rolfe and Lester Fuller features the variant “you can never tell a book by its cover.” The phrase has remained a popular expression to this day.
As mentioned earlier, the saying don’t judge a book by its cover is an idiom. An idiom is an expression with an intended meaning that typically can’t fully be understood just by looking at the individual words that comprise it. Even if you’ve never heard the term idiom, you have most likely heard many idiomatic expressions. Here are just a few of the most common idioms used today:
You’re in hot water.
His boss gave him the ax.
It’s time to face the music.
You’ve hit the nail on the head.
If you took the first example literally, you’d think it was describing a person standing in a bathtub full of hot water, perhaps. But the expression is actually used to describe a person who’s in trouble. Likewise, rather than literally being handed a tool for chopping wood, if you get the ax from your boss, it means you’re getting fired. It’s time to face the music means that it’s time to come to terms with the consequences of your actions. And when someone has hit the nail on the head, they’ve gotten an answer exactly right or done something exactly as it should have been done.
This idiomatic expression is a little different from others, in that you can understand at least a portion of its meaning just by taking it at face value. Yes, it does mean that you shouldn’t judge a book by its cover: It may have an ugly cover but be a wonderful book, or it may have an interesting and intriguing cover but be a boring and dull read. But you now know it’s typically used, as idioms are, figuratively, to apply to all types of things and to people as well. The metaphorical phrase means that you can’t tell a thing’s value or a person’s characteristics and qualities just by outside appearance alone.
There are a variety of sayings with a very similar meaning to don’t judge a book by its cover. For example, looks can be deceiving, things aren’t always what they seem, and the idiom and proverb all that glitters is not gold.
Discover many more idioms and proverbs here.
The common saying and English idiom don’t judge a book by its cover or can’t judge a book by its cover means that you shouldn’t form an opinion about a person, place, or thing just by looking at their or its outside appearance. After all, you can’t tell what a book will be about just by glancing at its cover, just as you can’t know someone’s personality, characteristics, and qualities based just on their looks or the worth or value of an item solely considering that thing’s appearance.
