I mentioned finishing this book [1] recently. The book also had a final short section on the author's methodology which in some ways was as interesting as the rest of the book.

Basically, don't trust what people say, even the people who were there!

For example three participants in the early days of RPGs gave three different accounts of the introduction of polyhedral dice into wargames. In the end Peterson reconstructed what history he could from articles Gygax wrote at the time.

Anyway, from now on this will completely change how I read any book called "An oral history of...". I mean, I already knew that personal accounts of events a mere 10 or 20 years ago can be very unreliable, but it was good to see actual examples in writing.

[1] Playing at the World (2E) Volume 2 by Jon Peterson