an open book, he/she is (like an)(redirected from he/she is an open book)
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.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
an open book, he/she is (like an)
Very obvious. See read someone like an open book.
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer