Discussions like this often seem to presume that there was an idyllic time, somewhere in the past, when kids' books were substantially better, or when young people read great adult literature. Graham contrasts Percy Jackson and Riordan's new encyclopedia Percy Jackson's Greek Gods to the classic 1925 collection of Greek myths by Ingri and Edgar D'Aulaire. She finds Riordan's book slangy and "inscribed with obsolescence," since it references Craigslist, iPhones, and other pop culture detritus. The D'Aulaires, on the other hand, remain "lucid"—though their poetic Victorian language is, she admits, "stilted." Graham seems to conclude that it's a loss that kids want to read lines like "At first, Kronos wasn’t so bad. He had to work his way up to being a complete slime bucket" instead of “In olden times, when men still worshiped ugly idols, there lived in the land of Greece a folk of shepherds and herdsmen who cherished light and beauty."

To me, though, Riordan's joke about Kronos is actually better written: less weighed down with reverence, more surprising, and less condescending towards its subject matter (who is it who sees those idols as "ugly"?). I read Riordan's The Lost Hero multiple times and worked on a study guide about it; I wouldn't say that its prose is deathless, but I can think of many inferior books. Percy Jackson isn't any worse than the Hardy Boys adventures or Piers Anthony's Xanth novels that I read as a kid.

For that matter, Ebony Elizabeth Thomas, assistant professor at the University of Pennsylvania’s Graduate School of Education, told me, "When people say children's literature isn't that great, a lot of adult literature isn't that great." Better Percy Jackson than 50 Shades or John Grisham or the Left Behind books. Better Percy Jackson than James Fenimore Cooper, for that matter—or than The Old Man and the Sea. Inventive, goofy, elaborate adventures with gods and gleeful pop cult references—or maudlin, macho themes shamelessly vaunting simplicity as an anxious marker of seriousness? I'll take the first, thanks.

I'm sure that comparing Riordan to Hemingway is going to cause a certain amount of wailing and denunciation. But that's the thing about aesthetics; there isn't a single standard, or a single agreed-upon rubric for what is "good." Graham tentatively suggests that the Percy Jackson books are too beholden to their own time, and timelessness or universality is, of course, often used as a measure of quality. But it's not a very convincing measure.

As just one example, most of the classic children's literature books—Alice in Wonderland, Peter Pan, Narnia, Treasure Island—look very dated today by virtue of their overwhelming whiteness, their time-bound, helpless inability to imagine that people come in more than one skin color. Rick Riordan, in contrast, takes care in his books to include heroes of many ethnic backgrounds: Hispanic, black, Asian, and Native American, as well as white. Children of the gods in his novels also often have learning disabilities; dyslexia is seen not as a failure, but as a mark of specialness or heroism. Thomas told me, "I do think that [Riordan] does a better job with diversity than some of the middle-grade texts I grew up with," and she added that the books were very popular among her nephews and nieces, and among the middle-school children she works with in Philadelphia. Riordan has a more thoughtful, original, aesthetically considered take on issues of marginalization and diversity than do the D'Aulaires, or for that matter, than does Hemingway. It seems likely that many kids take that into account, in various ways, when they respond to his books. Should we really be so quick to assume that their taste is debased?