Read this as a kid, and didn't get it. Upon rereading, it's kickass.
The first section belabors very well a nice joke from Kuhn's Structure of Scientific Revolutions
, proposing a change to the physics of the universe, building an elaborate Tesla-style economics on them, and then exposing how no one wants to alter the physics, even when faced with certain death, because that would require alteration of the economics.
The middle section switches to some weird aliens with trilateral sex lives, similar to Butler's in Lilith's Brood
, though with a different emphasis. The section demonstrates that the communications from the aliens, subject to interpretation in the first section, are premised on something completely different than what the interpreters believe. It's a nice critique of scientific interpretation.
The third section brings it back to humans, and presents an updated version of Pascal's Wager, wherein a scientist admits that he can choose to believe that the high tech in section I is Evil, be wrong, and lose nothing--or can believe it's not Evil, be wrong, and destroy the universe. Again, the critique of scientific interpretation is manifest.
I'd've appreciated a more ambiguous ending, which would be more consistent with the ambivalent presentation of the sciences and scientists. All of the "hard scifi" content is great--Asimov is nothing if not a master popularizer. The middle section was a bit more labor-intensive, because the aliens are very alien.
Definitely worth the Hugo and Nebula it won, even though I'm not quite sure how to interpret the title, which is taken from a Schiller play.
Recommended highly for left-emotionals, one-man revolutionaries, and those who know that prudery is the other side of prurience.