In his chapter on Love, Piper gives this helpful definition:
Love is the overflow of joy in God that gladly meets the needs of others. (119)In his chapter on Money, he rebukes materialism, saying:
God is not glorified when we keep for ourselves (no matter how thankfully) what we ought to be using to alleviate the misery of unevangelized, uneducated, unmedicated, and unfed millions. The evidence that many professing Christians have been deceived by this [wealth-prosperity] doctrine is how little they give and how much they own. God has prospered them. And by an almost irresistible law of consumer culture (baptized by a doctrine of health, wealth, and prosperity) they have bought bigger (and more) houses, newer (and more) cars, fancier (and more) clothes, better (and more) meat, and all manner of trinkets and gadgets and containers and devices and equipment to make life more fun.
They will object: Does not the Old Testament promise that God will prosper his people? Indeed! God increases our yield so that by giving we can prove our yield is not our god. God does not prosper a man's business so he can move from a Ford to a Cadillac. God prospers a business so that 17,000 unreached peoples can be reached with the gospel. He prospers a business so that twelve percent of the world's population can move a step back from the precipice of starvation. (198)
By the way, this book and many others are available free online at www.desiringgod.org