There are many expressions commonly used in English to express similarity.
There is no magic rule to help you remember them. You just have to learn them. Sorry!
Take a look at the examples below.
To read someone like a book.
If you can read another person like a book, you can very easily analyse and understand them – especially their emotions, intentions and motivations.
E.g. He always knows when I am lying. He can read me like a book.
To be like an open book.
If someone is like an open book, they are very open, honest and their feelings can be easily interpreted by others. They are easy to understand and have no secrets.
E.g. Her life is like an open book. She is very honest and has nothing to hide.
Have fun learning English!
Louise