I *love* reading, and so does my brain. 'Book crazy' is scarily close to a good description at times...Yes, I love reading in that crazy zombie/daydreaming/psych-eval needing half-awake/half-in the world of the book kind of reality- and I like it that way. Sometimes, however, this leads to 'reading' because despite having physically put the book down, my mind is still 'reading' the story.
By 'reading', you'll note that I'm referring to the way my brain cannot process the fact that the book is gone and so it makes up it's own continuation of the plot as a kind of soothing balm to cover this strange mental 'wound' caused by the sudden removal of a world that it was kind of into. Sometimes this can last five seconds. Sometimes, this leads to me writing fanfiction. Sometimes it hovers in the background until I can pick up the book again and finish it.
I've used this as a measure before, to evaluate a good writer/author/novel/series. The authors that have sent me deepest down the rabbit hole have often become favorites, and gone on to sell thousands (or more!) copies. Conversely, when I hear that someone 'can't put a book down', I have been known to ask if they have thought about the plot once they have been forced to put the book down- if yes, then I'm much more likely to take the recommendation seriously.
I love my mini-escapes into fictional worlds, and that books can give us this opportunity to expand the imagination. I also like the perspectives this can force us to consider, as we relate more closely to characters and gain deeper understanding of their motives, and within this, our own lives. Perhaps the brain is the key link between books and movies; providing a middle ground or personal cinema service that a good book can work with in order to motivate further consideration and visualization, and an even deeper 'reading' and learning experience. All I know is, my brain can take a good story and run with it- as far as I need us to go.