re: what to read

Rules of Play: Game Design Fundamentals, by Katie Salen & Eric Zimmerman and A Theory of Fun for Game Design, by Raph Koster both are excellent reads which are also frequently adopted as textbooks for academic courses in game design theory. Other than that it kind of depends on the specific topics you're interested in the most, but I really think those two books will be more than enough to start (as the amount of info in there is pretty amazing too). If you're looking into tips on how to approach game design for tabletop RPGs, I would also consider buying a whole lot of actual board games (not only in that specific genre, and definitely don't limit yourself to the most popular ones) to thoroughly and methodically analyze and dissect how those have been crafted, how they play, how they work, etc. Chances are you will learn a whole lot of things by doing that alone, many of which no book will ever teach you.