Definition
Describes a person whose thoughts and feelings are easily known or understood by others.
形容人很坦白，容易被人看透
She never hides her feelings; she's like an open book.
她从不隐藏自己的感受；她就像一本打开的书。
He always expresses his opinions openly; he is truly an open book.
他总是公开表达自己的意见；他确实是一本打开的书。
Although she is shy, her expressions are very obvious; she is completely an open book.
虽然她很害羞，但她的表情非常明显；她完全是一本打开的书。