Here are some ways to break down the meaning:
* "Read" refers to the ability to understand and interpret information.
* "Like a book" implies that the information is readily available and easy to grasp.
So, when you say you "read someone like a book," you are essentially saying that you know them so well that you can predict their actions and reactions effortlessly.
Here are some examples of how the idiom is used:
* "I've known her for years. I can read her like a book."
* "He tried to hide his true intentions, but she read him like a book."
* "Don't try to lie to me, I read you like a book."
The idiom is often used in a positive way to indicate a close and understanding relationship, but it can also be used in a negative way to suggest that someone is being manipulative or untrustworthy.