A hook is what makes us curious and keeps us reading in the opening pages of a story. In the first few pages of A Wrinkle in Time, we're introduced to an important story arc, the disappearance of Meg's father, which, of course, makes us curious and drives the rest of the plot. But I would argue that the more important initial story hook is the more generalized sense of mystery, of which the missing father is only a part. Opening with "it was a dark and rainy night" is a cliche, but also signals a mystery, as does Fortinbras's barking, which he only does when a stranger is approaching the house. Then there's feisty Meg feeling like a misfit, the mysterious little brother Charles Wallace waiting for Meg in the kitchen, and the glamorous mother. In a story that's as much about the characters as the adventure, it is ultimately our curiosity about the unusual but close-knit family and what is going to happen to them that hooks us and keeps the pages turning.