/u/kieslowskifan has written on Shirer before here which they concluded with a sentiment I personally share as well:

The long and the short of it is there are many, many books on the Third Reich available to readers in 2017. Many of them do a much better job of explaining the dictatorship far better than Shirer. To rely upon a book published in 1960 that presented an outdated and flawed view of Germany even at the time is simply a folly.