Wow. Since I come from a country where book reviewers are only allowed to employ approved phrases of Correct Criticism, I can only say,
"A master at the height of his powers."
That's my judgment of the book by its content.
In order to assist those who must judge On Blue's Waters by its cover, I merely give my assurance that yes, the guy in the boat with the funny creature on board does indeed meet a naked young blonde woman sitting on a rock in the sea. The inaccuracy of the illustration is that the man should not have a full head of hair. It's important, and that's why it took Gene Wolfe to write it.
"Have I said that time turns our lies into truths?" (The Shadow of the Torturer, ch. 17 "The Challenge", end of chapter)
-- Dan Rabin
*This is WHORL, for discussion of Gene Wolfe's Book of the Long Sun.