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

Example Sentences

The commemorations in Ashdown Forest to mark Pooh's 100th birthday are expected to include an installation, which would transform the forest's visitor centre into a life-sized pop-up book.

From BBC • Dec. 24, 2025

The pop-up book offers as immersive a tour of the house as you can dream of.

From Los Angeles Times • Jun. 9, 2025

There have been many editions of Carroll’s proto-psychedelic saga since it was first published in 1865; but this pop-up book, illustrated and engineered by Robert Sabuda, is particularly amazing.

From New York Times • Mar. 11, 2023

Groups are led into “A Midsummer Forest,” an installation filled with oversize illustrations from “A Knavish Lad,” a pop-up book based on “A Midsummer Night’s Dream.”

From Washington Post • Jul. 21, 2022

There might be a neat pop-up book, or a dinosaur diorama that I could add to my collection.

From "It All Comes Down to This" by Karen English