read somebody like a book
US /riːd ˈsʌm.bə.di laɪk ə bʊk/
UK /riːd ˈsʌm.bə.di laɪk ə bʊk/

1.
把某人看得一清二楚, 完全了解某人
to understand someone's thoughts, feelings, and motives very well, as if you are reading a book
:
•
She knows me so well; she can read me like a book.
她太了解我了;她能把我看得一清二楚。
•
After years of working together, I can read him like a book.
一起工作多年後,我能把他看得一清二楚。