Not an engaging story. It plods along, dabbles in a boring romance plot, and tries to pull off a series of twists at the end that just don't work. And the final reveal is insultingly obvious. There is some dangerous document teased a few times in the book, which has apparently been lost or hidden:
He told us specifically that it was the most dangerous document he knew. You remember what he said. I can quote it. He said, 'The matter is death for the Tyranni, and death for those who use it as well; but it would mean final life for the Galaxy.’
This quote occurs not thirty pages into the story, and at that time I noted, "Surely Asimov isn't going to pull out the declaration of independence, or something like." Two hundred pages later, the very last paragraph of the story reveals that the document is… the US Constitution. Splendid.