BTW, Jon Peterson, the scholar linked to by the OP, has written an amazingly great book about the history of D&D. (If your definition of “amazingly great” encompasses “containing insane levels of detail”).
His book, Playing at the World is 720 pages long! In it he exhaustively details the various strands that came together to produce Dungeons & Dragons, covering both the history of wargaming and the history of fantasy literature. What’s wonderful about it is that he just doesn’t say, “this happened, then this happened, then this happened”. He’s reconstructed a history of influences, using original sources (zines, letters, private notes) to show where different elements of D&D originated and how Gygax, Arneson and the rest came into contact with them.
For example, the origin of the thief class can be traced to homebrew rules developed in spring of 1974 by a group playing at Aero Hobbies in Santa Monica. The idea was passed along in a phone call from the owner of Aero Hobbies to Gygax. Gygax wrote up initially released the thief rules in a small low-circulation zine before rolling them into Greyhawk, the first supplement. Peterson goes step by step through all the surviving documentation of this chain. It’s totally insane and really fascinating.