I've only read first and second editions. There wasn't much difference between the two, other than 2e added a token chapter on digital prototypes.
I describe the book this way:
* The first third of the book is just laying down the terminology and concepts of the field. It's necessary, it's dry, and it's mostly a repeat of the same portion of every other competent game design textbook ever. And I agree that the procedure vs. rule distinction is foggy and not really that relevant to practical game design (I can make games just fine without remembering the difference in the book, and I remember struggling with that same thing when I first read it years ago). Looking it up online, the distinction is that what Tracy calls "procedures" are like the printed rules of a board game, defining the setup / initialization, rules of play, special cases, conditions of resolution, and determining outcome. Rules specifically govern player behavior, what the player can and can't do. So "avatar jumps when player presses A and they were standing on the ground" is both a procedure and a rule, "player can press A at any time and as many times as they like, whether it does something or not" is a rule but not a procedure, and "avatar starts on the extreme left side of each level" is a procedure but not a rule, would be my understanding. But I tell students they don't need to know the distinction. (I prefer talking about the three kinds of rules from Rules of Play in this context, as those distinctions are easier to justify.)
* The last third of the book talks about the game industry, and feels very out of place in a textbook on game design - it'd be like having chapters on major biotech corporations in a cell biology textbook. It also struck me as pretty basic stuff that any student should hopefully know BEFORE they commit to a four-year undergrad degree in games (though I admit that not all of them do). Most of the time I just want to rip the last third out and pretend it didn't happen.
* The middle part is the meat of the book and worth the price of admission. Most design texts either don't mention rapid prototyping and playtesting and iteration, or mention it in an offhand "yeah, this is super important, you should make games that way" sort of way. This one goes into deep detail with the why and how-to, giving the best treatment I've seen in any book to the subject of how to make a paper prototype quickly and run a competent playtest session to answer critical design questions.
Guest interviews in game design books (in general) are usually not there for people like us :). They are there so that beginner-level students give the book some legitimacy in their minds, that it's not just a textbook written by some know-nothing academic, it's written by someone who knows what they're doing and is backed up by other people who know what they're doing.
- Ian