I'm not sure if I can add much more to this particular book than what I said about the game system in my comment on the Players Handbook. However I have noted that TSR (which is owned by Wizards of the Coast which in turn is owned by Hasbro, and I can see how Wizards of the Coast easily made more money than TSR because Magic the Gathering is much more like crack than a roleplaying games) do tend to release their books with a separate Gamemaster's and Players book. However, I do note that the Gamemaster's books tend not to have all that much in it that really do add to the rules.
Okay, they may contain monsters, but who cares if you know what the monsters stats are (though surprise special abilities may add to the flavour) because that generally does not help you when you are in combat, and even then seasoned players tend to know all of the monsters off by heart anyway. However, the gamemasters books do tend to contain information which does really help run a game so you end up having to fork out another $60.00 for another book (though Magic the Gathering is a much better syphoner of money).
Personally I really can't remember what is in this book, though I suspect that it is still lying at the bottom of a crate in a shed at the back of my parents house 700 km from where I am writing this review (and the car trip takes about 8-9 hours, which the plane flight, including the time it takes me to leave home and get to the city (45 min) catch the airport shuttle bus (45 min, plus $15 ticket) to the airport, hang around the airport (1 to 1.5 hours) and then get on the plane and wait for it to take off (15 mins) and then fly to Adelaide (45 min), and then go from the airport to my parents house (45 min), it would bring the total up to 4 hours, so, as I have just proven, planes may be faster, but they are not all that fast (and somebody even suggested that using the same calculation, it is faster to get to San Fransisco by car than it is by plane, though only just).
Well, I've just spent an entire paragraph talking about anything but this book, but as I said, there is little I can say about this book that I have not said in the commentary on the Player's Handbook. Anyway, the only reason I ended up getting it was because it was going cheap (most likely a clearance sale). It never really took off, though I think I did try running a couple of games. However I can't remember how well it worked, and I must admit, I do prefer d20 Modern (and Future) though I only played a few sessions of that as well.