
An open book
Predictable Personality
Refers to someone whose thoughts and actions are easy to guess.
As soon as he heard the news, I knew he would offer to help; he's an open book.
No Secrets
Describes someone who doesn’t hide their feelings or secrets.
You can ask her anything, she’s an open book.
Emotional Transparency
Indicates that a person's emotions are easy to read and understand.
After the match, his disappointment was an open book.