How Do Stories Shape Our Self Identity?

Well I personally know a person that was so into a book that basically everything she said for like a whole year was from the book she read

i personally saw this as pathetic

but to more answer your question it depends on how much you let a book or movie define you to know if it will shape you too much or not

Stories be it in the form of a book or a movie takes us into a different world altogether. Real life stories or biopics (fictional stories with roots on reality) can make us enlightened about the trials, tribulations, romances, tragedies, adventures, thrills and victories about famous and infamous personalities.  Similarly fantasy stories, poems, horror-stories, erotic novels, children's fables, sci-fi tales or any other work of literary work can also influence our thinking. What we are is a consequence of our thoughts. Stories form a part of our subconscious and we begin to relate episodes and incidents in our life to stories that we have read or watched.

When we are children, we delve into the fantastic world of Alice in Wonderland and Snow-white and the seven dwarfs. At that time we live in the fear of a witch or an elf. As we grow up, mature and understand the world around us, we generally begin to read more novels, detective stories and thrillers. Our outlook changes as we drift from a witch, an elf or demon to the archetypal villain, a smooth operating criminal or a spooky creature lying in a super-natural world. We soon begin to attach a "genre" of book we specially like to read. Some of us immerse ourselves in philosophical books and spiritual tales. What we read forms a part of psyche, our self-identity and we begin to look the world with the relevant perspective.