His Dark Materials — Philip Pullman

Philip Pullman's trilogy (1995-2000), beginning with Northern Lights (The Golden Compass in the US), is the greatest fantasy written for readers of all ages — a profound, Milton-influenced critique of institutional religion and authoritarianism built on a multiverse of parallel worlds, armoured polar bears, and daemons (animal embodiments of the human soul). It remains one of the most banned book series in American school libraries.