What is the author's style in Lincoln at Gettysburg: The Words that Remade America by Garry Wills?

Wills' style is difficult, often for no reason. His sentences are overly long and he chooses words of many syllables when shorter ones would do. He is at his best when he is making a short dramatic point and when he allows his passion for his subject to show:

"(Lincoln) came to change the world, to effect an intellectual revolution. No other words could have done it. The miracle is that these words did. ... At Gettysburg, he wove a spell that has not, as yet, been broken."