Pullman's work is often compared to C.S. Lewis's because he's a fantasist who's interested in religion, but the His Dark Materials trilogy has a unique setting and a strange internal logic all its own. Pullman's world resembles Victorian England, running on clockwork and steam, but it is dominated by an awesomely powerful church called the Magisterium. Also, everyone in Pullman's world has a constant companion called a daemon, a creature who exists as a kind of animal expression of that person's soul. Some readers may find the intricacies of Pullman's plotting, and his determined critique of organized religion, to be a little exhausting in the later books, but there is no denying the power of Pullman's visual imagination, which runs to huge dirigibles and armored polar bears. The film version, starring Nicole Kidman and Daniel Craig, is due this December.