Were it not for the world of the dead, though, the third book would quite probably have been irredeemable to me. Gah. Well, no. The world of the dead and Mary's adventures with the Mulefa. The Mulefa were way cool. But the rest of it? THEY"RE THIRTEEN, FOR CRYING OUT LOUD! No one discovers their one, true, undying, passionate love when they're THIRTEEN! That whole 'omgsotragic' ending was practically Romeo and Juliet, except instead of dying they both got to live long, happy lives. And we all know how much I love R&J.
In short, the trilogy as a whole are not the worst books I have ever read. (That honor, by the way, belongs to a book I read in sixth grade. 'somethingsomething Gods.' No, I don't remember the title. To this day, it remains one of three books I could not bring myself to finish after I started reading it. The other two being Diary of Ann Frank and Mary Shelley's Frankenstein.) But they definitely didn't live up to expectations, and they definitely aren't even close to ranking among what I consider the best of YA fiction. Sorry, Pullman, but Susan Cooper you ain't.
YMMV, of course. Feel free to discuss.