Here are a few things I'm interested in from this book: 1) general intellectual history; 2) the history of existential risk; 3) a chance to meditate on history / civilizational development in general; 3) a chance to meditate on existential risk; 4) engage with Moynihan's "seeing existential risk is a sign that we are mature" idea.
I think I got all of those.
I don't think I'll try to read it twice, unless it seems like a good idea once I get through it once. It's a history book and not a philosophy book.
I only read it once, as predicted. Actually, I found the philosophy (and futurist) parts of it the most interesting and useful to me, page for page. But that's not unusual, because I am more interested and educated in those subjects than in history. Futurism is somewhere between philosophy and history (a kind of speculative history). So it talks about change and events, but is imaginary, rather than based in pre-existing evidence. The history I found myself reading through as "material". I think that probably the history was where Moynihan was "earning his keep", and so he had to provide more details, ones which perhaps to a historian evaluating Moynihan's story would have seemed necessary, but which were a bit more than necessary to support Moynihan's futurism. That's not a criticism of Moynihan, but a report of my experience.
Perhaps in an ideal universe, I would have found a more philosophy- or futurism-oriented book to work against, rather than a history book with philosophy and futurism in it. Maybe in the future... But if Moynihan did a good job representing the beliefs of a large-enough segment of the intellectual culture (for instance, certain of the transhumanists or other atheistic futurists), then I think his book would have to have been a valuable one for me to read. It may be just as well that I got a version of transhumanism and longtermism intended for a more-general audience, with history, futurism, and philosophy related to each other in one book.
I recently read Unbelievers by Alec Ryrie, and it also struck me as being a history book that was trying to do philosophy (or in Ryrie's case, perhaps some psychology). Both books did some preaching, subtly or not. History is an art form, I guess.