I read Jon's book Playing at the World last year.
I will eventually review it here. But, to do the book justice, the review will take time and consideration that I haven't yet had. In short, the book is a masterwork that few people need to read. However, I will argue that the limited size of the book's audience doesn't diminish it. Jon applies a method and care that obviously comes from a well of personal passion, and not from external motivations. In many ways Jon's project reminds me of tabletop roleplaying itself. Much time and effort is devoted to a good game, particularly on the part of the Game Master. It is a process that brings rewards that are only appreciated from participation on the inside. IMHO past times of this nature have lost favor to those wrapped in the predominant merits of popularity and external affirmation.
I gamed with Jon in a group in Boston in the late 90's. A couple of other people on this site were in that group. I won't 'out' them. Jon and I were never close, and I haven't seen him since. However, I remember hearing that Jon was working on this project more than a decade ago. So often you meet people that intend to do a number of things. It's nice to see when intentions are realized, and Jon's book far exceeded any expectations I might have had.
Update: Jon is currently doing an AMA on Reddit. http://www.reddit.com/r/IAmA/comments/1w7x3r/i_am_games_hist.../ Gave a shout out to my game, Wayfarers. :)