an open book, he/she is (like an)

be an open book

1. To be easy to understand or decipher. I wish these legal contracts were an open book.
2. To act (or purport to act) honestly, with no secrets. Ask me anything, I'm an open book. Adam says he's an open book, but I've seen him sneaking out of his house late at night.
See also: book, open

be like an open book

1. To be easy to understand or decipher. He said these instructions were like an open book, but I can't make sense of them at all!
2. To exist, respond, or act honestly, with no secrets. You can ask me anything you want—I'm like an open book. You can always tell when Sarah is upset. She's like an open book.
See also: book, like, open
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

an open book, he/she is (like an)

See also: he, open, she
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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