Most people know John Piper as an advocate for what he calls 'Christian Hedonism'. He famously summarizes this philosophy with the phrase, "God is most glorified in us when we are most satisfied in him". With a reputation for being a Christian hedonist, it might seem odd that he would write a book on the spiritual discipline of fasting. But if you start to wonder about that, read his definition of Christian hedonism again. Piper isn't arguing that God is glorified simply by our satisfaction. Rather, God receives glory when we realize that we can only find true satisfaction in him.And fasting teaches us to find our satisfaction in God better than just about anything.At this point, let me make a quick note for all those - like me - who don't agree with Piper theologically. Piper is a strong Calvinist. I'm not. And if you're not either, you may be wary of reading this book. Don't be. Piper's Calvinism doesn't make many appearances here. This is a practical book, and though Piper's assumptions may shine through here and there, he's willing to make statements like, "the fasting in Acts 13 changed the course of history." So if certain elements of Piper's theology has turned you off, don't let that keep you from benefiting from his writing on more practical subjects.A Hunger for God is worth reading for every Christian - Calvinist and non-Calvinist alike.Piper begins his study on fasting with a chapter that I initially found somewhat odd - but which made sense to me after the fact. He asks the question, "Is fasting Christian?" Throughout my Christian journey, I've immersed myself in authors who focus on spiritual disciplines (Richard Foster, William Law, Dallas Willard, etc.). I've read several books on fasting. And I've always been intrigued by the various accounts of fasting in Scripture.So for me, asking, "Is fasting Christian?" is like asking, "Is praying Christian?" or "Is helping the poor Christian?" Of course it is! There's no question. But the fact is, for many people there is a question. They look at verses like Mark 2:18-20 and assume that Christian fasting only took place between Jesus' death and resurrection. Or they find some other verse, pull it out of context, and assume that Christians are beyond fasting. *Spoiler Alert* They aren't.In this first chapter, Piper acts as a gentle guide. He acknowledges the objections that some have raised to fasting and then points to the scriptural reality. There are a few places where, in my view, he's a little too generous. For example, he writes, "the prevalence of fasting in the Old Testament raises the question whether the practice has abiding validity for people who live on this side of the coming of the Messiah and the appearance of the kingdom of God." And though some may raise the question - I don't see how fasting's Old Testament prevalence necessarily raises it. Especially if you've ever read the New Testament. Fasting appears often in the New Testament.So through this chapter, Piper walks the middle of the road. In fact, there were moments here when I wondered if he believed fasting was important, or even useful. But eventually he made his way to the important conclusion that "in this age there is an ache inside every Christian that Jesus is not here as fully and intimately and as powerfully and as gloriously as we want him to be. We hunger for so much more. That is why we fast".And with those words, he hits the ground running.In the rest of the book, he looks at the practice of fasting from a variety of different angles. He discusses how fasting reveals our truest desires, how it helps us set our houses in order, and how it gives us the opportunity to draw closer to God. Then, he examines Jesus' experiences with and teachings on fasting. There's also a great chapter on how fasting points us toward the culmination of the Kingdom.Throughout this book, Piper calls all Christians to hunger more fervently for God and for his will to be done on earth as it is in heaven. This is a call that needs to go out day after day after day. For too long, Christians have become fattened on spiritual junk food. They've been told that God wants them to have health, wealth, and prosperity. They have believed that comfort and wordly happiness is the pinnacle of human satisfaction. But those are lies. And fasting lays them bare.Piper ends his discussion on fasting with a chapter that, again, I initially found peculiar. It's titled, "Fasting for the Little Ones: Abortion and the Sovereignty of God Over False Worldviews". "What does abortion have to do with fasting?" I wondered. But after reading it, I believe it serves as a fitting conclusion. Piper recognizes that too many evangelical Christians have put all of their eggs in the political-activism basket. They've said, "If only we can elect a Christian president..." or "If only we can move the Supreme Court to the right...". But forty years have passed since Roe v. Wade. And what do we have to show for all of our effort?Barely anything.And the changes that have occurred (such as the percentage of pro-life people increasing in our country) haven't come about via political pressure. They've largely happened through individual relationships. And, I'd argue, the prayers of God's people.I'm not saying that Christians shouldn't engage in the political process. I believe they should. But ultimate transformation - the kind Christians long for - won't take place through legislation or the courts. It will only take place through a move of God, motivated by the cry of his people.And though my understanding of God's sovereignty is different from Piper's, our actions must be the same: recognize God's authority in the world, fast and pray for his hand to move, and act when he calls us to. This is the only way that we'll see the Kingdom advance in our world.A couple of final thoughts on A Hunger for God. Love him or hate him, Piper can be incredibly quotable. And this fact is evident throughout this book. There are a number of lines that scream to be pasted on a background and shared via Facebook. For example:"The greatest enemy of hunger for God is not poison but apple pie.""The birthplace of Christian fasting is homesickness for God.""The more deeply you walk with Christ, the hungrier you get for Christ.""When we are living in sin, the fast that God chooses is not a religious covering, but a direct frontal assault."This is good stuff. And since fasting is such a neglected spiritual discipline, I'm thankful that Piper threw his rather large hat into the ring by writing this book. Hopefully more people will recognize the value of Christian fasting because of it.May we all - Calvinist, Arminian, Catholic, Orthodox, and everyone in-between - long for God and his Kingdom together, through the precious, biblical practice of fasting.