Mage first Edition is quite a game book. I will openly say that I'm just not a fan of it, and that if this was the first Mage book I'd seen, I wouldn't be neck-deep in the game to this day.
That said, about half of this book worked. Unfortunately, it was the underdeveloped half. The rest included things like the Technocracy interrupting their REM sleep so they wouldn't dream, the Void Engineers being Fae-touched and wanting to kill space, and the generally overwhelming nature of the Technocracy against the much less gray than later Traditions.
What did work though were things like study points (they dropped from Mage and now Mage is known as an XP sinkhole because it was balanced assuming them), the basic premise of a war for reality, and the mechanical effects of various foci (which could have been brought back in M20 with the Instruments, but weren't).
Overall, it's a playable game, but not one I'd want to play, and I'm glad that Mage Revised was my first Mage book.