[watwut]

William Shirer did not went through all that material. He was journalist and not historian.

If you are interested in result of going through all that material, read Richard Evens trilogy.

[scrumper]

I'm confused by that - the book is absolutely crammed with footnotes, references to, and direct quotes from that archive of material. Undeniably, Shirer editorializes - he doesn't write like a historian - but his book is absolutely firmly based on that material. He even says as much in his introduction.

But thank you for the other recommendation.