"It's his favorite"

Some time ago I wrote a post about how the book "Where The Wild Things Are" represented Sam's journey with autism to me.  Since then my Sam has chosen this as his favorite book.  When I say favorite, I mean to say that he eats with his book, he sleeps with his book, he rides in the car with his book, he carries his book to therapy 5 days a week, he plays with toys on top of his book, he looks at other books on top of his book.   If Sam is upset we can recite his book to him and he calms immediately, if you say any random line in his book he will immediately find the page.   It's his favorite.