In the heyday of Mage, the Void Engineers were the Star Trek Convention. Now, they're the Starship Troopers Convention. This book has two things that would make any Mage player want to pick it up. The first is a Cosmological breakdown of the Tellurian from a Technocratic perspective - and the Spheres needed to reach each of these places (all in one handy sidebar). The second is the system for creating Voidships. These two sections, alone, make the book worth it. And all the other bits of awesome top off the tank.
[Personal note: Thank you, OPP - I've been waiting ten years for THIS book. Totally worth the wait.]