Even a joyful holiday ballet like The Nutcracker nods gently towards madness, darkness, and fear: in the dangerous Mouse King, first and foremost, and also in the mysterious magician and uncle, Drosselmeier. E.T.A. Hoffmann’s story – on which it is based – tells a darker story than Tchaikovsky’s ballet. Darker yet is Gregory Maguire’s new novel Hiddensee: The Once and Future Nutcracker. “As evidenced especially …