What metaphors are used in Born on a Blue Day: Inside the Extraordinary Mind of an Autistic Savant by Daniel Tammet?

Books are a metaphor for comfort and meaning. Daniel is obsessed with books. One of his favorite places to visit to feel comforted is a library. As a child, Daniel would check books out of the library or spend hours pouring over dictionaries and encyclopedias. During his school years, Daniel spends his free periods in the library instead of interacting with his peers. His family's home is always full of books, and as a small child, he would stack the books in piles.