I've not read His Dark Materials
so, could you, you know ~ what sort of questions does His Dark Materials ask? The biggest question in Harry Potter is probably whether Prof. Snape is on the Order's side, the Death Eater's side, or his own side (given the progression of the Potter stories it would be arbitary I think, to ask whether Snape is good/evil. The stories have also raised loads of other questions about the series itself, and regarding more general issues such as the nature of death, the power of love (cheesy!) the nature of evil and morality...