A girl I once caught reading Fahrenheit 451 over my shoulder on the subway confessed: "You know, I'm an English lit major, but I've never loved any books like the ones I loved when I was 12 years old." I fell slightly in love with her when she said that. It was so frank and uncool, and undeniably true.

Let's all admit it: We never got over those first loves. Listen to the difference in the voices of any groups of well-read, overeducated people discussing contemporary fiction, or the greatest books they've ever read, and the voices of those same people, only two drinks later, talking about the books they loved as kids. The Betsy Tacy Books! I loved those books! The Wonderful Flight to the Mushroom Planet! I can't believe you know that! The Little House on the Prairie books! Oh, my God--did you read The Long Winter? So good. Hey--does anyone else remember The Spaceship Under the Apple Tree?

It's not just that these books, unlike adult literature, have been left unsullied by professors turning them into objects of tedious study. We love these books, dearly and uncritically, the way we love the smell of our first girlfriend's perfume, no matter how cheap or tacky it might have been. Let's be honest: We all know that Ulysses and A la recherché du temps perdu are "better" books than The Velveteen Rabbit or The Little Prince, but come on--which would you take with you on a spaceship to salvage from the dying Earth?

Let me put it another way: When was the last time a book changed your life? I don't mean offered you new insights or ideas or moved you--I mean profoundly changed the way you see the world or shaped the kind of person you are? If you're like me, it's been longer than you'd like to admit. I recently read Eli Sagan's Cannibalism: Human Aggression Cultural Form, which enabled me to see capitalism as a highly sublimated form of aggression, on the same continuum as headhunting, warfare, and slavery, and Marcus Aurelius' Meditations, which gave me a greater equanimity about the esteem of others and assuaged my fear of death. But if I ever end up holed up in my parents' farmhouse holding off the bulldozers with a machine gun while listening to Beethoven's late quartets, it'll be because of the story "And the Moon Be Still as Bright" from Ray Bradbury's The Martian Chronicles.

About the last time in our lives when books have this kind of potent effect on us is in our early 20s, which not coincidentally tends to be the age of people you see poring over Nietzsche or that awful Ayn Rand. There's something alarming about this. I don't want to believe that our personalities ossify so much in adulthood that we're no longer capable of being changed by art. But part of the reason art loses its power over us, of course, is, simply and sadly, that we get old; our personalities, as soft, impressionable, and tempting as freshly poured sidewalk cement when young, gradually set and harden over the years with whatever graffiti passers-by scrawled there still indelibly inscribed in it. But when a 14-year-old gushes that the Twilight series are the best books she's ever read in her whole life, it's easy for grownups to forget that this is not necessarily hyperbole. At that age, we haven't heard any clichés, and even dumb ideas are new.

It's not that children's books are pure entertainment, innocent of any didactic goal--what grownups enviously call "Reading for Fun." On the contrary, the reading we do as children may be more serious than any reading we'll ever do again. Books for children and young people are unashamedly prescriptive: They're written, at least in part, to teach us what the world is like, how people are, and how we should behave--as my colleague Megan Kelso (The Squirrel Mother) puts it, "How to be a human being."

There is a level of moral instruction in these books underneath the incidentals of plot, character, and setting that we're constantly absorbing: How would a decent person act in this situation? What would a bad person do? What's the right thing to say to a friend when something terrible happens? The Lord of the Rings books are no more concerned with martial virtues such as loyalty and courage than they are with elaborate codes of courtesy and honorable conduct. Bridge to Terebithia makes this function of literature explicit when Leslie gives Jess The Chronicles of Narnia to read so that he can learn how a prince should behave.

"They're such moral books," Kelso says of the Little House series. "There's so much in them about how a good family should be, how communities help each other, the pioneer spirit, and the morality of the country." We're hardly even aware of this aspect of books when we're children because it's such a basic need; we're ravenous for this information. The exotic details of story and setting are like the sugary frosting on children's cereal; these lessons about life and the world are the real nutriment, the eight essential vitamins and minerals.

Of course, it's also in childhood that we're first exposed to some of life's big shocks and secrets--love and mortality. And the most terrible secret of all is the inevitable syllogism of these two: that the things we love will die. If we're lucky, the first loved ones we lose in this life are imaginary: Charlotte, Old Yeller, Old Dan and Little Ann (Where the Red Fern Grows), Flag (The Yearling), Aslan (though this is sort of a cheat since, like Jesus, he comes back right away), or Leslie Burke (Bridge to Terebithia).

"I think adults tend to forget about the fears of childhood," author Jenny Boylan (She's Not There and I'm Looking Through You) says via e-mail. "I was then and am now drawn to stories that paint a more complicated picture of childhood. Fern, in Charlotte's Web, is poised between childhood and adolescence--she starts off rescuing Wilbur from death (yes, that's right, DEATH WITH AN AX), and yet by story's end she kind of forgets about Wilbur--she and Henry are `off at the fair.' So to speak.

"At story's end, Wilbur's one friend--the wise, illuminating, literate spider--curls up and dies. Wilbur manages to save her egg sac, tends it all winter, and in the spring, the babies hatch out and--IMMEDIATELY LEAVE HIM. Except for a couple of them, who know nothing of Charlotte, and how she saved Wilbur's life. Charlotte's Web was the first book that made me weep, and I wept because I knew that it contained truth."

Sometimes we're not ready for the truths inside these books--they're trying to feed us ideas that are still bigger than our heads. A collection innocuously called The Golden Book of Fun and Nonsense became an object of hysterical fear for me because it contained a chapter of translated Struwwelpeter, those grim German verses about ill-behaved children (they refuse to eat soup, they slam doors) who meet with what are presented as well-deserved, fitting deaths (starvation, getting clocked by a marble bust). These stories are products of the same German child-rearing tradition that produced grownups like Hitler. This chapter had to be paper-clipped shut in order to render the book safe for me. It wasn't the specter of transgression and punishment that was so terrifying to me--it was the casual, brutal fact of death.

Kelso evokes the quality of those children's books that takes on an almost numinous power. "It's magic," she says. "It contains some secret special knowledge for you, and it gives a book a vibe, like it almost scares you, but you keep going back to it again and again." She cites one book that did affect her in adulthood as deeply, and in the same way, as the books that fascinated and frightened her when she was a child: The Face of Battle, by John Keegan, a reconstruction of what several famous historic battles must have been like for the soldiers who fought in them. "I keep going back to it, like it has something to tell me," Kelso says. Like children's books, Keegan is telling her one of life's terrible secrets, a secret about Men and Death that's completely outside her experience as a woman who's lived her whole life in (relative) peacetime.

Even as fully grown adults we remain secretly starved for guidance and instruction. Many of us are walking around with the uneasy feeling that we missed the first day of class and wondering if there are CliffNotes. Most people desperately want someone to tell them what life's about, what people are for, what we're supposed to do--how to be a human being. But serious literature, at least since the 19th-century, has been disdainful of fulfilling any didactic obligation. Sorry, kids, that isn't what art is for.

There is a kind of no man's land in the literary landscape that can't be called "children's" or "young adult"--it's recognized as serious literature, if a little patronizingly, by the adult world--but which has a specific and perennial appeal to adolescents. I'm thinking here of writers such as J.D. Salinger and Kurt Vonnegut Jr., those staples of the college dorm. We reserve a special reverence for these authors that is qualitatively different from the respect, even awe, we feel for undeniably great writers like Toni Morrison or Cormac McCarthy--it's less rational or open to critical discussion. The reaction to revelations of the usual mundane human failings in recent biographies of figures beloved from childhood, such as Ray Bradbury or Charles Schulz, has been not just the surprise or sad worldly shrug we might expect but hostility and denial--a sense that we ought not to have been told such things, as if we'd been told once more that Santa Claus wasn't real or Shoeless Joe threw the series. And Joyce Maynard and Margaret Salinger's troubling memoirs about Salinger--we didn't want to know. Salinger and Vonnegut both give voice to the adolescent passion for justice, their dogmatic, almost fanatical, fairness and decency, and their blooming disgust at the epiphany that the world adults are foisting on them is neither fair nor decent.

Meanwhile, books that unabashedly purport to supply all the answers sell like Hula-Hoops or Viagra. This genre is called "wisdom literature" if it's old enough to be respectable or "self-help" if it's by someone who's still alive and making money off it, and ranges in credibility and earnestness of intention from the Tao te Ching and Aurelius' Meditations to shameless dogshit like The Secret. "Religious" comprises its own category on publishers' best-seller lists, so mammoth and lucrative is this market.

I would suggest that the vast popularity of this genre is because it is effectively children's literature for adults. They address us directly, confidentially, allegedly explaining everything and advising us how to comport ourselves correctly. Even cynical hoaxes (or, to give them the benefit of a doubt, artifacts of clinical delusion) such as The Celestine Prophecy, The Da Vinci Code, and The Shack partake of--or exploit--that same thrill of being let in on a secret, the shiver of magic you remember from the first time you walked farther back in the old wardrobe than the wardrobe went and felt the furs turn to firs against your cheek, or glimpsed an old Victorian house in the fog where none had been the day before, or saw an unearthly glow over the hill out in the old apple orchard. Titles such as The Secret, The Rules, and The Game pretty much say it all: Someone's finally going to initiate us into the select society of Those in the Know, for only $23.95 retail.

These books also frequently appeal to some authority higher than that of mere fellow human beings: the ancients, beneficent aliens, or good old God. (This is how sacred texts always establish their authority: Hey, I didn't make this stuff up; I just wrote it down.) When we're children, all the books we read are handed down to us, like the Ten Commandments, by grownups, who seem like, and sort of are, a different order of being from ourselves. They're the gods of childhood, bigger and older and more experienced; they know more than we do, imparting what wisdom to us they think we can bear, empowered to tell us what to do. I'm over 40 now, no longer by even the most charitable definition a young adult, and I'm starting to realize, in something like panic, that I don't understand anything, and that nobody else seems to know any more about it than I do. There aren't any grownups. And maybe there aren't any secrets left to tell.