I'm pretty sure I put this book on my get-at-library list thanks to this Reason plug from Ron Bailey back in 2019. (The list is slow and occasionally leaky, but eventually…) The author, Laurence B. Siegel, is currently affiliated with the CFA Institute Research Foundation; it is devilishly difficult to find what "CFA" stands for, but I think it's "Chartered Financial Analyst".
Siegel is a qualified optimist; he sees a rosy future ahead for the world, if we don't screw it up. The book is © 2020; things seem to have gotten somewhat less rosy in the interim, but we are talking long-term trends. Still…
Siegel and I share a number of reliable sources: e.g., Matt Ridley, Deirdre McCloskey, Steven Pinker, … And even quotes from a Robert B. Parker novel on page 323! While not overtly political, he's very much a "three cheers for free-market capitalism" kind of guy. Well, maybe 2.7 cheers; he notes that unrestrained businessfolk will tend to exploit negative externalities, if allowed.
The book is very wide-ranging and eclectic. The "fewer" in the title refers to population: Siegel notes that the "population bomb", so popular a doomsday scenario just a few decades ago, has been defused in the developed world; and there's no reason to assume this won't eventually envelop the entire world. Unlike some, Siegel sees this demographic shift as a favorable trend. (He goes into quite a bit of detail on sensible retirement planning in such a scenario, one of his fortes.)
He goes on to explain the "richer, greener" part: essentially, there's no reason to suspect that continued growth and innovation won't eventually benefit everyone; it's a positive-sum game. And richer societies can afford to invest in environmental protection. And, unless the naysayers have their way, nuclear power can easily help us wean off of fossil fuel use. He is very entertaining describing the "ecomodernist" vision.
There's a neat picture of the Boston Treepod proposal, which seemed to be a big thing back in 2011, and then … as near as I can tell, nothing since. It's a variation of my own semi-crackpot Idea That Could Save Everything: artificial photosynthesis, pulling CO2 out of the air, combining with water and sunlight, producing oxygen and carbohydrate. Except doing it scalably and far more efficiently than natural photosynthesis, i.e. plants. Siegel, bless him, comes closer to describing my vision that I've seen elsewhere.
Siegel's style is informal, chatty, and discursive; the book often wanders in unexpected directions and interesting asides. Recommended!