Open Book, an

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Meaning of Idiom 'An Open Book'

An open book is someone or something that is easy to understand or interpret; clear; straightforward; easy to solve; an honest and frank person. 1,2,3

See the related idiom read someone like a book.

See the antonym a closed book.


This expression, alluding to a book lying open so that anyone can easily read it, is usually used to describe a person, especially their feelings or thoughts.

"The famous CEO always seemed to be an open book so everyone was very surprised to hear about his dark secret."

"Marcus can never hide his true feelings. His face is like an open book."

"My whole life has been an open book," said the actor, "but now I want to settle down to a quiet life of my choosing."


Related to the expression "read someone like a book," variations of this idiom have been used since the mid-1800's. 2

1. Kirkpatrick, Elizabeth M. The Wordsworth Dictionary of Idioms. Ware: Wordsworth, 1995.
2. Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013.
3. Jarvie, Gordon. Bloomsbury Dictionary of Idioms. London: Bloomsbury, 2009.

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