open book

American  

noun

1. someone or something easily understood or interpreted; something very clear.

   The child's face is an open book.

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open book British  

noun

1. a person or thing without secrecy or concealment that can be easily known or interpreted

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open book Idioms  

1. Something or someone that can be readily examined or understood, as in His entire life is an open book. This metaphoric expression is often expanded to read someone like an open book, meaning “to discern someone's thoughts or feelings”; variations of this metaphor were used by Shakespeare: “Read o'er the volume of young Paris' face,” (Romeo and Juliet, 1:3) and “O, like a book of sport thou'lt read me o'er” (Troilus and Cressida, 4:5). [Mid-1800s] For an antonym, see closed book.

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Etymology

Origin of open book

First recorded in 1850–55

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Example Sentences

See Examples For:

open book

Rayan Cherki refuses to hide his emotions, an open book for all to see and hear in times of joy and disappointment.

From BBC ● Aug. 28, 2026

The back features a genie’s lamp resting on an open book and a feathered quill with an olive branch in the background—symbols of peace, knowledge and learning.

From The Wall Street Journal ● Feb. 4, 2026

She’s an open book in interviews — she’s an open book everywhere.

From Los Angeles Times ● Dec. 17, 2025

"We're a very open book in this family," she said.

From BBC ● Sep. 2, 2025

Cara tried to smile back but shivered instead, and forced her eyes back to the safety of the open book on her desk.

From "The Landry News" by Andrew Clements

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