This is by far the best of Asimov's empire novels, and I think it may be his best science fiction novel. It is suspenseful, fast paced and the main characters are mostly well-developed (the one exception to this is the main female character -- Asimov could not write women).

The book is set on the worlds of Florina, the only place in the galaxy a gorgeous form of cotton called kyrt can be grown, and Sark, the overlords of Florina. Sark controls Florina and kyrt production by the most in humane methods. A lone-space traveler carrying the secret to Florina's future and the key to kyrt production lands on Sark and then disappears, setting off the mystery around which the rest of the story is built. Sark/Florina politics are complicated by the fact that Trantor controls half the galaxy and would like to control it all, forcing the actors to take interplanetary politics into account when planning their every move. The action moves fast and the story is internally consistent. I highly recommend this book.

[note: this is a re-read for me]