Inspired by the review on letsrun.com I purchased the book.
On the very opening pages the author presents world best time at marathon for the 50th ranked comparing year 2015 (or 2016) with 2019. He then goes on to say that the 1.30 to 2.00 min improvement (he found) is not that big.
Correct me if I am wrong but I thought that was a pretty decent improvement. Maybe I am missing something since English is not my first (or even second) language.
Maybe the author could have gone further back in time and made comparisons between 2011 and 2015, e.g.
Otherwise I am thrilled to continue reading the book as it looks promising.