If you ask me (which nobody did, but hey, bite me), I don't think that section is necessary anymore. Let's be realistic. Any product that we, as hobbyists, make is for hobbyists. That's the simple truth, and has a couple of important consequences, the most important of which is that you're writing to people who already know the subject matter. The guy who's wondering what an RPG is, is not opening up your self-published book and reading what you wrote there.
That guy has either already picked up an RPG (probably Dungeons and Dragons, but possibly a White Wolf game or some other mass-produced game you can pick up at your Large Bookstore of choice) and read what they had to say, or he's been taught by somebody who already knows what's up. Our hobby is fairly unique in that it rarely spreads by the raw materials. Usually, it spreads, memetically, through people. You get taught by some guy, who got taught by some other guy, and so on and so forth, until you get to people who either taught themselves with a mass-marketed game's introductory product, or you get to Gary Gygax, Dave Arneson or whoever.
These people don't need introductions. The purpose of an introduction to "shared make believe time" has already been served. You don't need to do it.
I mean, really. Is there anything more of a waste of space than including how to roll dice and which way to round numbers? If somebody's reading, say, my Aremorican Addendum, they already know how to roll dice and what character sheets they're using and which edition of D&D they're grafting it onto. They know what hit points do, and what spell levels are, and the difference between divine and arcane magic is. You don't have to explain that any more than a magazine aimed at aviation buffs needs to explain what in the world a "bushtail lightwheel" is. You already know, or you wouldn't be here.
Computer games don't come with instructions on how to right click and drag things anymore. You don't have to explain the basics of a 30 year old hobby to people. You're writing to an advanced audience. You don't have to pretend otherwise.