I wrote the comment below over a year ago, about how these popsci books are very unreliable sources of knowledge because of the perverse incentive structure (eg would this book have been written if the conclusion was 'we don't know how important sleep is, but it seems generally pretty important although this is difficult to prove and largely obvious'). It was downvoted pretty heavily.

https://news.ycombinator.com/item?id=18244061

I mean, none of this is surprising.