The aptly-titled “Instructions” plays with the typical fairy tale structure. Mr. Gaiman uses very spare prose to remind readers of all the twists and turns that await those who travel on the path or stray from it. This is a book that is and isn’t a story, is whimsical and sober at once, playful and cautionary. The illustrations by the incomparable Charles Vess are a wonderful accompaniment, with surprises and secret details sprinkled here and there throughout the pages. A tree does not merely shelter an old woman but harbors crows above her head and hidden creatures with glowing eyes in its roots. Take heed, travelers, and beware of wolves.