It's also ONLY an engine - there is not a single word in the book describing a specific campaign setting. But it's the cleanest, easiest, most logical design I've ever seen. Greg obviously put scads of thought into the system, adding nothing unless it was necessary. He also exhibits an extremely dense writing style.
Character creation is quite detailed.
Attributes and stats are bought with separate sets of points, with 100 AP and 50 SP defining a fairly average human. Most attributes give a low level of aptitude in related skills, making skill purchases slightly cheaper. Skills are cascaded, with Primary, Secondary, and Tertiary skills. Since a lower level can never be more than half the next higher level, you want your Primary skill to be as high as possible. I was surprised by the skill system.