The real meaning of the title The Best of All Possible Worlds doesn’t become apparent until the end of the book. Nevertheless, Karen Lord makes a strong case from the beginning that Leibniz’s pronouncement is correct, although whether it’s because of Caretakers, angels, or simply the strong anthropic principle might ultimately be left up to you. Science fiction likes to tantalize with the prospect of alternative realities—and it is a great idea, to be…