What does your child can read you like a has been out to grass idiom means - see Roger Waters' song Hello I Love You?

The idiom "can read you like a book" means that someone can easily understand your thoughts or emotions, often because they are transparent or predictable. In the context of Roger Waters' song "Hello I Love You," it suggests a deep emotional connection where one person is so familiar with the other that their feelings and intentions are clear. This understanding can evoke feelings of vulnerability and intimacy, highlighting the dynamics of human relationships.