John Piper is obviously a man who loves God and has a heart and skill for teaching. I've watched some of his sermons and read a couple of his books and have a great deal of respect for him. My challenge is always in his extreme saturation with Calvinism. As someone predestined to be a non-Calvinist it makes it a challenging read to strain out the TULIP from the wheat. That said, I can always learn and grow from someone who desires God as much as brother John does and I will continue to try and work my way through another one of his books soon.