Best to let the Kid know about god and all that as early as possible I suppose.
But seriously His dark materials is a great set of books but I'd recommend it to very few twelve years olds.
I have two sets of the books currently lent out to people (one i'll never see again) . On another note his Grimm fairy Tales is a fabulous book with really good insights and backgrounds. Well worth it.
And giving the local catholic priest a copy of Jesus the Goodman and Christ the Scoundral is always good for a laugh
'There is no future for e-books, because they are not books. E-books smell like burned fuel.'
Ray Bradbury (RIP)