Having seen the film "The Golden Compass" ( based on the book the "The Northern Lights" - 1st book in the trilogy) I wished to know more of the overall story - which may or may not be committed to film.
I then enjoyed reading the trilogy "His Dark Materials" ( see seperate review) but wanted to delve more deeply into the thinking behind the book(s).
For those wishing to get further background to the books , the story ( an apparent orphan discovering the identity her parents and the world of adults in a semi victorian universe starting in Oxford - with a repressive and inquisatorial religious system ), the science ( parallel universes , "dust" and dark matter) and the history ( comments from Pullman himself), this provides an excellent pocket guide at a reasonable price and indicates other sources ( books , websites) where more information can be found.