It's at the bottom of the article, but I think it's worth noting that Jon Peterson does some impressive work for role playing game historical documentation. His book Playing at the World is a labor of love, giving not only a detailed history of the early days of wargames and tabletop rpgs, but a history of the science fiction and fantasy genres, a history of games in general, and how those lead to the creation of modern rpgs. He then wraps things up with a chapter on how tabletop gaming influenced the star of the video game industry.

The scope is huge, the book is giant, and he published it under his own imprint so that no one could tell him to cut things. I found the section on Kriegsspiel particularly interesting. Highly recommended if you're an enthusiast for the subject, otherwise you'd probably get very frustrated.