open book

noun

(idiomatic) Something of which salient aspects are obvious or easily interpreted.

She is an open book.

意味（1）

(idiomatic) Something of which salient aspects are obvious or easily interpreted.

There is one, with a dark and thoughtful eye,

Who is to all others a mystery;

But his soul is to me an open book,

And I read his mood in his slightest look; ...

意味（2）

(idiomatic) A person who through naivete responds candidly to questions or openly displays their emotions or intentions.

意味（3）

(mathematics, topology) An open book decomposition.

意味（4）

(climbing) An inside angle in the rock.