We had we had just marked up the final, hard-copy proofs of the book and had taken them to a FedEx office in London to have them sent to the publisher in the United States. We sealed the manuscript in the FedEx envelope and started filling out the waybill: address, sender, nature of contents, and so on, until we came to the question “value of consignment.”

Unsure of the exact value of our package, we left that question unanswered. “You can’t say ‘zero,’ ” said the FedEx clerk. “US Customs might think that’s weird and hold up the delivery. What is it you’re sending?”

“A printout of our book,” we said.

The clerk picked it up. “Pretty heavy block of paper,” he said. “I’ll put down £5.”

It couldn’t have been more ironic that here we were, puzzling over the relationship between a pile of paper and an intangible asset—the ideas in a book—and having trouble valuing it. It was a reminder that often you can appreciate things fully only when you experience them.

Our learning process continued after the hardback version of the book was published. Tyler Cowen of Marginal Revolution developed our ideas of how intangible investment could lead to secular stagnation, and expressed them with more clarity than we managed. Similarly, the Time’s Danny Finkelstein and Financial Times’s Martin Wolf gave us new ways to communicate our “four S’s” framework for the economics of intangibles. The Economist’s Buttonwood columnist pointed out that the rise of intangible-based companies might radically change equity markets, creating a small elite of outperforming stocks, and Chris Dillow of the Investor’s Chronicle worked through some of the implications for investors.

At talks at Nesta, Google, and the Conference Board, people raised with us the idea that blockchain technology could help manage the spillovers of intangibles and lay the foundations for new economic growth. Speaking to public policymakers at the UK’s Treasury and 10 Downing Street, at the OECD, and in Washington pushed us to think about the consequences of intangibles for governments.

One event in the news was particularly illustrative of the problem of measuring and valuing intangibles: the bankruptcy of the British outsourcing and construction firm Carillion. You would think that Carillion, known as a building company, would be the very embodiment of tangible capitalism: surfacing roads, putting up office blocks, using huge diggers: all very solid stuff. After all, they used to be called Tarmac.

Amazingly, they turned out to be nothing of the sort. Not long after Carillion went bust, financial journalists pointed out that its balance sheet contained £2bn of (non-cash) assets, of which 75%, around £1.5bn, were intangible—specifically, goodwill. Commentators asked what these intangible assets were and why they had proved so evanescent.

In fact, this was a model lesson in how unsatisfactory company accounting standards are in representing intangible investment. As we had learned, for the most part company accounts ignore intangibles. But they make an exception when one business buys another: in that case (to simplify slightly) the difference in value between the price paid to acquire the company and the book value of its assets is turned into a single intangible asset, called goodwill, and put on the acquirer’s balance sheet.

This asset does not relate to any specific intangibles like R&D or designs or business relations of the sort we describe in the book. If anything, it more closely resembles a financial asset (the implied value of the securities of the acquired company) than it does a productive one. Goodwill, then, is a very different type of creature from the intangible assets we talk about in this book, and the fact that it alone of all intangibles gets capitalized by company accounts is a further sign of the gap between company balance sheets and the types of assets that really matter in today’s economy.

We are excited to see Capitalism without Capital out in paperback and to have this opportunity to thank everyone who was kind enough to spend time reading and commenting on the hardback. We hope that this will spark a wider discussion about what the rise of intangible investment means for the welfare of society, public policy, managers, and investors.