Most of the cost of an iPhone derives not from the materials and labor used in assembling it but from the ideas, or intellectual property, underlying its fabrication. The importance of such intangible inputs, as epitomized by smartphones, is an increasingly prevalent characteristic of the modern economy, but one accompanied by a disturbing slowdown in the growth of productivity. In this thought-provoking book, Haskel and Westlake attribute this slowdown—along with other economic problems, including rising inequality and the mushrooming of monopolies—to a mismatch between institutions and policies that were created for the era of tangible capital, on the one hand, and the needs of the intangible economy, on the other. The authors’ proposals for resolving this conflict are wide-ranging. They suggest changes in financial regulations to permit insurance companies and pension funds to invest in high-risk intangible assets, so as to finance and thereby encourage their development. They also recommend that governments alter patent protections to prevent firms with intellectual property from having to expend resources in fighting patent thieves.