Few friendships have had such far-reaching implications for the world—from finance to technology to philanthropy—than that between Bill Gates and Warren Buffett. After meeting at a party in 1991, the two played cards and golf, shared jokes, swapped trade secrets, ate junk food, talked and listened.

Their growing friendship would impact each man and lead to change on a grander scale, culminating in the development of the Bill and Melinda Gates Foundation, which holds nearly $50 billion in assets. How did such an unusual union blossom? In what ways specifically did each man begin to influence the other? How did these two avid wealth accumulators jointly decide to address some of the world’s most critical problems—poverty, disease, inequality—by giving their wealth away?

And what, finally, does their giga-wealthy partnership mean for the rest of us in an age of great wealth—and great inequality? This book gives the fullest account yet of this extraordinary relationship and explores how it has transformed these two men—and is changing the world for the better for all of us.