Earlier quoted context omitted.
This is a very popular and quite detailed pop science book on sleep written by a prof of neuroscience: https://www.goodreads.com/book/show/34466963-why-we-sleep
This book actually gets quite a lot of hate on HN as parts of it have been debunked (or are at least heavily argued about): https://guzey.com/books/why-we-sleep/
To be fair though (not that it excuses it) but pop-science/livestyle book written by academics to gain more notoriety usually suffer from this issue that a lot could be fixed by doing X. Livespan by David Sinclair also does this by basically pinning everything on aging.
It makes for a good read but I think it's best to always keep a healthy skepticism.