Here's a breakdown:
* "Read" implies understanding or deciphering something.
* "Book" represents a structured narrative with clear intentions and predictable outcomes.
* "Like a book" compares a person to a story, suggesting that their personality, habits, and motivations are easily deciphered.
Here are some examples of how the idiom is used:
* "I can read you like a book. You're clearly nervous about this presentation."
* "My best friend knows me so well, she can read me like a book."
* "After years of working together, I can read my boss like a book."
Essentially, the phrase suggests that you've developed a deep understanding of someone's personality and behavior.