It depends on what you mean by “dreadful”! Paul Spears explains why Harry Potter is dreadful and vulgar and that’s a good thing. It’s all in Chesterton, says Spears:

So much of what is considered important and thought provoking in sophisticate literary circles is really just a veneer over truly despicable ideas….

It is good that Harry Potter is dreadful and vulgar. It appeals to those of humanity who, according to Chesterton, “have never doubted and never will doubt that courage is splendid, that fidelity is noble, that distressed ladies should be rescued, and vanquished enemies spared.”

Made my day! Now I’m off to see Stardust—which I hope will be similarly “dreadful” in a good way.