On the right you have a controversial and strict idea of "how to use the language properly" from an inspirational and influential member of the community and on the left you have a "deep dive into the language".

To make it interesting, Crorckford (The Good Parts) actually referred to Flanagan (The Definitive Guide) as the only non-awful book in the subject out there..

My take on it? Two excellent books, just read them both and use your own judgment ;)