in one's book

in (one's) book

According to one's opinion, judgment, or code of personal ethics. In my book, it's worse to run away from a fight than to start one. You kissed a girl, even though you have a girlfriend. That's cheating in my book, dude.
See also: book

in one's book

According to one's opinion or way of thinking. For example, In my book he's a wonderful father. This expression alludes to a book containing a personal list of some kind. [Slang; mid-1900s] Also see black book.
See also: book