Seated on a gold throne with plush red cushions, Rowling read a passage from the seventh and final of her novels on Hogwarts School of Witchcraft and Wizardry, "Harry Potter and the Deathly Hallows."
She then took a dozen pre-selected questions from the dressed-up and dazzled kids and teens.
To accommodate a crushing demand for tickets for her first American appearance since 2000, Rowling's American publisher sent a "sorting hat" like those used to divide students into houses in the novels to 40 randomly selected Los Angeles schools. Forty students from each school were then selected from the hat.
Rowling said the gimmick was meant to avoid the sort of madness she faced in her last U.S. appearance seven years ago.
"Things had gotten a little unmanageable signing-wise in the terms of the numbers who were turning up," she said, "but I really missed being able to interact directly with readers."
All 1,600 students received a signed copy of "Deathly Hallows."
Rowling, a former schoolteacher, took the stage to a thundering, shrieking ovation, then said: "It wasn't like this when I was a teacher. If it had been, I might never have left."
When inevitably asked what she might be writing next, Rowling said only that.
"I think probably I've done my fantasy," she said. "I think because Harry's world was so large and detailed and I've known it so well and I've lived in it for 17 years, it would be incredibly difficult to go out and create another world."
The reading was part of a weeklong visit by Rowling to the states known as the "Open Book Tour."
She'll also appear in New Orleans on Thursday and in New York, at Carnegie Hall, on Friday.