I started looking for this, the first book in Pullman's "His Dark Materials" series, after seeing it on a few lists of books/films/music which also contained a number of my personal icons, so I had every expectation of enjoying it, and it is very good; though it's ostensibly 'childrens' literature' (Paradise Lost-referencing series title notwithstanding), I imagine that a large part of these books' fanbase would be people in similar headspaces to myself.
The basic genre is fantasy, and it's pretty heady stuff given its supposed target audience (which is all to the good) - not as dark as the Borrible trilogy, say (though, on the evidence of Northern Lights, equally good), but a significant step further into the shadows than the Harry Potter books (not that I've read beyond halfway through the first of those). The reader spends a large part of the first fifty pages or so in the dark as to what's going on (a deliberate move on the author's part), but once things begin to coalesce, they do so richly and satisfyingly, gradually revealing the breadth of Pullman's imagination. The plot moves forward at a fair clip, aided by crisp, largely cliché-free writing and good dialogue, and the characters are unobtrusively but fully drawn. I have a feeling that the series has been quite acclaimed; if so, then the pundits have definitely got it right with this one.