Definition of an open book in English:

an open book

phrase

  • A person or thing that is easy to understand or about which everything is known.

    ‘her mind was an open book to him’
    • ‘A lot about my life has been an open book.’
    • ‘Why, my dear fellow, I've read you like an open book.’
    • ‘Once they find out what I do, they become an open book.’
    • ‘His all-business assistant kept her life very private, while Jon's life was an open book to her.’
    • ‘Paradoxically, she is an intensely private person, yet lives her life like an open book.’
    • ‘We must be an open book to one another in marriage.’
    • ‘Her face was an open book to anyone who knew how to read her.’
    • ‘Only to close friends am I an open book.’
    • ‘Their personal life, it would be fair to say, is not an open book.’
    • ‘This conspiracy is, of course, an open book to God.’