"Know like a book" is a familiar phrase that indicates complete and thorough knowledge of something. There are plenty of synonyms that can be used in place of this phrase, such as "know inside out", "know by heart", "know backwards and forwards", "know like the back of one's hand" and "know like the palm of one's hand". All of these expressions convey the idea that a person knows something exceedingly well, whether it is a person, a place, or a piece of information. These phrases are interchangeable and can be used depending on the situation or the context in which they are being used.