IF their children start behaving strangely, adults might say, “Oh, Peter (or Jenny) has an imaginary friend.” Strictly speaking, this is true, but for kids, imaginary friends can be as real as school or the family car. Children’s imaginations are intense (强烈的), and Neil Gaiman, a British author, pays homage (致敬) to them in his writing for the young, nowhere more so than in his now-classic The Graveyard Book (2008).