# open book

idiom

Source: https://englishreference.com/idiom/open-book
Updated: 2026-08-10

## Meaning

Something whose salient aspects are obvious or easily interpreted.

## Examples

- He is an open book, so you always know his thoughts.
- Because she is such an open book, her friends can tell immediately when something is bothering her.
- Despite his attempts to maintain a stoic facade, his expressive face made him an open book to anyone who cared to observe him closely.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.