Five hundred years ago, working from hints in classical Greek and Latin poets, the young author Jacopo Sannazaro crafted the book called Arcadia, a narrative in richly descriptive Italian prose interwoven with elegant and passionate poems. A young man--transparently a stand-in for the author--leaves his home in Naples to join a community of shepherds in the remote Greek region of Arcadia. Yet he finds that this seemingly idyllic land is as...