Has anyone read the comments American reviewers have left on Amazon.com? Go there, select the reviews under the paperback copy of Northern Lights, and select the 1-starred entries. It makes some entertaining reading - my personal favourite quote being 'I would not give this book to any child or teen you want to have a tolerant attitude toward other's beliefs'. 'Beliefs' are naturally unspecified, but I'm pretty sure Pullman levels many of his comments at organised religion, which in itself isn't tolerant - the irony astounds.
Of course, you could then go and compare this to the British and otherwise reviews on Amazon.co.uk, where the religious controversy takes a backseat to concerns about the quality of narrative. Intriguing.
Also, I can't recommend enough the new edition of Milton's Paradise Lost edited by Pullman. It's only just come out in lovely hardback form, and everyone should buy it :)