an open book

USAGE SUMMARY

"an open book" is a perfectly acceptable phrase in written English.
You can use the phrase to describe a situation or person who is transparent, easy to read, or straightforward. For example, "He was an open book; I could tell immediately that he was not telling the truth."

✓ Grammatically correct

News & Media

Wiki

Academia

Human-verified examples from authoritative sources

Exact Expressions

48 human-written examples

Iago's an open book.

The Guardian

The night is an open book.

The New Yorker

Our life is an open book".

The New Yorker

It was an open book".

The New Yorker

Ms Yellen's views are an open book.

The Economist

Because I'm not -- an open book.

The New York Times

Human-verified similar examples from authoritative sources

Similar Expressions

12 human-written examples

– It's an open-book test.

University of California, Berkeley

It is an open-book, open-notes exam.

Stanford University

Zingerman's has always been run in an open-book fashion.

Forbes

First of all, during an open-book test the book is allowed during the entire exam.

BMC Medical Education

Each knowledge test has a closed and an open-book component.

Advances in Health Sciences Education

Expert writing Tips

Best practice

In professional settings, use it to describe transparency in processes or financial records to build trust with stakeholders.

Common error

Writers sometimes use the phrase in contexts involving actual literature without clarifying the metaphor, which can lead to ambiguity. For example, saying a library is "an open book" might be interpreted literally. Ensure the context clearly points toward transparency or vulnerability.

Linguistic Context

The phrase "an open book" typically functions as a noun phrase used metaphorically. In most cases found in Ludwig, it serves as a complement to a linking verb (e.g., "is", "seems", "remains"). Ludwig AI confirms its status as a correct and highly productive idiom in modern English.

Expression frequency: Common

Frequent in

News & Media

65%

Wiki

15%

Academia

10%

Less common in

Science

5%

Formal & Business

3%

Encyclopedias

2%

Ludwig's WRAP-UP

The phrase "an open book" is a robust and versatile English idiom verified as Correct by Ludwig AI. It is primarily used to denote transparency, honesty, and accessibility of information or character. Analysis of real-world examples shows it is a favorite in top-tier journalism, appearing frequently in The New York Times and The New Yorker to describe public figures and complex situations that have been laid bare. Whether you are writing a character study or an editorial on corporate transparency, using this phrase provides a clear, evocative image that resonates with a broad audience.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

a transparent person

More literal and often used to describe someone's character specifically.

easy to read

Focuses on the ability to perceive someone's emotions or thoughts quickly.

no secrets

Directly emphasizes the lack of hidden information rather than the ease of perception.

crystal clear

Commonly applied to situations or explanations rather than human personalities.

straightforward

Suggests honesty and lack of complexity in behavior.

an open scroll

A more poetic or archaic variant of the same metaphor.

plain as day

An idiom emphasizing that something is obvious to everyone.

unveiled

Implies that information that was once hidden has now been made public.

sincere

Focuses on the genuineness of the person rather than their visibility.

an open record

Shifted towards a legal or administrative context involving public documents.

FAQs

How to use "an open book" in a sentence?

You can use it as a predicative nominative to describe someone, such as: "He is <a href="/s/an+open+book" target="_blank" rel="alternative">an open book; he tells everyone exactly what he is thinking."

What does it mean if someone is "an open book"?

It means the person is very transparent, honest, and does not hide their feelings or past. They are <a href="/s/easy+to+read" target="_blank" rel="alternative">easy to read by others.

What can I say instead of "an open book"?

Depending on the context, you might use terms like "<a href="/s/transparent" target="_blank" rel="alternative">transparent", "<a href="/s/guileless" target="_blank" rel="alternative">guileless", or "<a href="/s/candid" target="_blank" rel="alternative">candid".

What's the difference between "an open book" and "a closed book"?

While "an open book" signifies transparency, a "<a href="/s/a+closed+book" target="_blank" rel="alternative">a closed book" refers to someone or something that is mysterious, private, or impossible to understand.