open book

noun

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

   The child's face is an open book.

open book

noun

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

Word History and Origins

Origin of open book¹

First recorded in 1850–55

Idioms and Phrases

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 .

Example Sentences

We’re kind of like an open book and the chapter hasn’t been written yet.

From Washington Post

Couple that with the digital breadcrumbs we actively share about the diets we try, the shows we binge and the tweets we love, and our lives are an open book.

From Science News

John Huston recalls in his autobiography, An Open Book, a time when he asked Mitchum to crawl across the grass on his elbows.

From The Daily Beast

It seems that Open Book Toronto has now included the entire entry.

From The Daily Beast

Good luck with that once your origins are an open book to officialdom.

From The Daily Beast

Schoolchildren today take open-book tests or with a calculator.

From The Daily Beast

When you contemplate running for president, your life becomes an open book.

From The Daily Beast

He lifted his head, looked around him, and was just going to switch off the light, when he noticed the open book on his table.

From Project Gutenberg

In the light of that astounding discovery, she now read the mysterious Dr. Weirmarsh as she would an open book.

From Project Gutenberg

Quickly I lean over; the open book in my hands entirely hides the keys.

From Project Gutenberg

His sad countenance, like theirs, was an open book in which the Russian could clearly read this important fact.

From Project Gutenberg

Three days later, Eustace, writing alone in the library at night, saw it sitting on an open book at the other end of the room.

From Project Gutenberg