be a closed book

To be difficult to know or understand. She's such a private person that I don't know much about her. I guess she's a closed book. I'm a scientist, so art will always be a closed book to me.

be a closed book

to be something that you know or understand nothing about (usually + to ) I'm afraid physics will always be a closed book to me.

Common Names:

Name	Pronounced	Usage
Zowie	ZO-ee	English (Rare)
Luana	loo-AN-ə (English), loo-AH-nah (Italian)	English, Italian, Portuguese
Funske	FUNS-kə	Dutch, Limburgish
Ragnvald	-	Swedish, Norwegian, Danish
Arcelia	-	Spanish
Milivoj	MEE-lee-voi (Croatian, Serbian)	Croatian, Serbian, Slovene, Medieval Slavic