Philip Pullman explictly says his fantasy trilogy (I seem to remember reading somewhere that he doesn’t like it to be called “fantasy,” but fantasy it is, however he feels about it) is an atheistic answer to Lewis’s allegorical and Christian Narnia series.
I enjoyed His Dark Materials for the most part, but I think Catherine Seipp has perfectly captured my feelings on how the two stack up against each other (and note I would never have thought of stacking them up against each other if Pullman hadn’t made a point of how much he detests Lewis and everything Narnian):
I’ve read the Narnia series repeatedly over the years…But leaving religion entirely out of it, I can’t imagine reading the Pullman books again. This doesn’t mean I wasn’t glued to them when I discovered the series a few years ago, but while Pullman’s imagined worlds are powerfully eerie, his characters are flat, humorless and generally annoying. Maybe in a generation or two Pullman will prove to be as enduring as Lewis, but I doubt it. Until then, though, I envy the child who hasn’t read either series yet, and receives a boxed set of both for the holidays.