Interesting. Learned new facts about Agatha Christie. But, it's good to note this was published in 1975, so some have been refuted since this was written. Interesting, esp the ongoing discussion about the origin and evolution of mysteries starting w Poe. Good info about other authors throughout her life, competitors, friends, etc.
I found this disappointing. The first half of the book essentially re-works the life of Agatha Christie, and the second half charts the development of the detective story/mystery thriller. I was expecting more.