No clear favorite, since the whole series really is one big book, but I will say that the first book is tops for me by a smidgen, because if I hadn't liked the first book, I wouldn't have gone on to the others. I devoured the whole book in a little less than two hours, caught up in the suspense of it all. I can't say the same for the others, though they did have more character development and deal with weighter issues than the first one.