I was first made aware of Pullman's series by a friend of mine, C, who is a teacher and was concerned because the book might be pulled from her school's library. Well, if so it would be in good company I suppose - banned books are frequently good reads. (YMMV) When I heard that Pullman's book was being challenged due to it being anti-religious, I decided to read it myself. My son is interested in this book too, and I like to pre-read what he wants to read when I can.
The book does take an anti-religious tone, but I didn't see the cause for offense for any religious people today. The anti-religious sentiment in the book is analogous to the anti-empire sentiment in Star Wars; it moves the plot along, but I find it doubtful that young readers would become inspired by the book to overthrow religious institutions by it. After all, no empires were toppled by any Luke wannabes after the Star Wars series was released in the 70s, and it had a far greater audience.
What did bother me was the portrayal of parents in the series; anyone who had the misfortune to be a parent was either evil, cowardly, ineffectual, or a victim. The childless adults were more interesting. That seems like rather a flat portrayal of adulthood and parenting.
Otherwise, the children heroes are lively, have credible motivations and are a delight to read about. Lyra is a heroic girl of the 'spunky princess' variety. Will as the protagonist serves as the wounded rescuer in the midst of his grieving. Will offers a subtle philosophical distinction for readers to ponder, at a level that most children (and even a few adults) would understand -
"But there's my mother. I've got to go back and look after her. I just left her with Mrs. Cooper, and it's not fair on either of them."
"But it's not fair on you to have to do that."
"No," he said, "But that's a different sort of not fair. That's just like an earthquake or a rainstorm. It might not be fair, but no one's to blame. But if I just leave my mother with an old lady who isn't very well herself, then that's a different kind of not fair. That would be wrong."
Children struggle daily to determine what is right and what is wrong in a world that offers contradictory and confusing definitions of rightness. Will's definition of fairness is careful yet implacable: to be committed to being good is to do the right thing, even when wrong things abound and the situation isn't fair. That's a true and complex concept, and it is well explained in the book, in the quote above from The Amber Spyglass and throughout the series in the main character's actions. but
Phillip Pullman's His Dark Materials Trilogy includes The Golden Compass; The Subtle Knife; and The Amber Spyglass. Overall, I'd recommend the series, recognizing that a child reader will need some guidance in understanding the concepts discussed in the book.