Shyamalan's Lady in the Water Book - IGN
On June 21, 2006, M. Night Shyamalan released Lady In the Water, a companion book that is intended to explain some of the mythology of his new movie, and just maybe, bring some of its sense of mystery into your home. As it turns out, however, the book is not quite as compelling a read - either as a pre-emptive textbook or straightforward suspense tale - as one might hope; running some 64 pages (and featuring approximately 65 actual words), the elusive tale of a sea nymph and her quest to return to the water feels painfully underplayed and underdeveloped on the printed page. That said, the book does indeed introduce the world of Lady in the Water, not that it matters much since he basically repeats this information verbatim during the opening credits of the movie. Specifically, it explores precisely who (or what) is a narf, a sea nymph who takes up residence beneath apartment-complex pools, and what transformation she initiates within normal, ordinary people who under any other circumstances don't believe in otherworldy creatures.
http://www.ign.com/articles/2006/07/20/shyamalans-lady-in-the-water-book