English phrase from drama scenes

What Does "firstly don't judge a book by its cover" Mean?

Learn what "firstly don't judge a book by its cover" means, when people say it, and how to use it naturally in English.

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Firstly, don't judge a book by its cover.

It means you should not form an opinion based only on appearance.

From I Think My Wife Wants To Kill Me S2, Episode 40

When do people say this?

Scene Context

He reminds someone not to judge others too quickly.

Usage Scenario

Use this as a general warning or reminder in everyday conversation. It is very common, but the 'firstly' makes this version sound a bit unnatural.

Better ways to say it

1
Don't judge a book by its cover.
2
You can't judge a book by its cover.
3
Don't judge people by how they look.

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What Does "firstly don't judge a book by its cover" Mean? - ReelFluent