Northern Lights was good, but the last book -- The Amber Spyglass...it depressed me beyond belief. bah humbugWhat a terrible ending. Will and Lyra >=(
The best book by Pullman is (imho) not any in his Dark Materials trilogy, but from the other series he wrote -- I don't think it had a particular name, and each book could be read on its own without the reader having to read the previous one. The best: "The Tiger in the Well." Absolute class. <3 Sally Lockhart and Dan Goldberg.