His Dark Materials is a trilogy by Philip Pullman. It contains the novels The Golden Compass, The Subtle Knife, and The Amber Spyglass.

These are some of the best young adult fantasy novels ever written. Each book is absolutely wonderful and unique, and worth reading multiple times. It's easy to see why, at just twenty years old, the series is considered a classic.

Not only is the writing quality fantastic, but the themes that take place throughout these books are very dark and heavy for "kids" books. Life, death, and purgatory is explored thoroughly, and its religious themes are quite blatant if somewhat controversial. Though these may not be suitable for very young children, teens and adults of all ages can certainly glean some enjoyment out of these books.

The Golden Compass was adapted into a feature film about ten years ago, but sadly it was not a very faithful adaptation, and it was not very good. Hopefully, one day, someone will adapt the trilogy into a show or film series that remains more thoughtful and true to the original.