In her books, there is this magical substance called Floo powder, a pinch of which tumbles characters topsy-turvy from one spot to another in a blur of motion. They arrive a little scuffed up and dazed, but essentially in one piece.

Joanne Rowling -- who goes by J.K. on her books -- and about 2,500 of her adoring fans felt like they'd just gone for a Floo ride Friday night in Santa Rosa.

The author of the phenomenally successful Harry Potter books spoke briefly and then settled in to sign as many books as her arm could handle at Maria Carrillo High School.

For Rowling, it was the penultimate stop on a three-week Floo trip around the United States, appearing night after night before standing-room-only crowds who want to be in the same room with the person who created such a vivid parallel world of magic.

Her three books, "Harry Potter and the Prisoner of Azkaban," "Harry Potter and the Chamber of Secrets" and "Harry Potter and the Sorcerer's Stone," are Nos. 1, 2 and 3 on the New York Times Best Seller list for fiction this week, an unprecedented accomplishment by any author on any of the newspaper's lists -- fiction, nonfiction, children's books or adult books, according to keepers of the lists.

"Well, there's quite a lot of you," Rowling said after she was greeted with a standing ovation and thunderous foot stomping in the stands. "Last time I came here there were only five people. Where were you all then?"

The "here" she referred to was the greater San Francisco Bay Area. Soon after her first book was published, before she and Harry became such celebrities, she received a less rousing reception at a bookstore in the South Bay, explained Richie Partington, children's book buyer for Copperfield's Books.

In an animated voice with north-of-England inflection, Rowling read from her second book a passage about Dobby, an elf-like creature "with bat-like ears and bulging green eyes the size of tennis balls." Dobby's voice, high and crackly and full of life through Rowling's tired vocal chords, sounded a little like Yoda from "Star Wars." It was just right, and you could almost feel the scrunched-in crowd relax with "Yeah-she's-the-real-deal" relief.

She gave a couple tips on pronunciation: "It's `Her-My-OhKnee,'" she said, about the female protagonist, Hermione. She has encounted some humorous variations on her trip around the United States. "Although my favorite was Hermie-One, I liked that one," Rowling said.

She wouldn't say much about the next book but she did reveal that one of the characters will die before the seven-volume series ends. "I won't say which one, but I will say one of them dies."

She said, contrary to rumors on the Internet, the fourth book will not be titled Harry Potter and the Quidditch World Cup.

"I don't know what it will be called but it won't be that," Rowling said.

"It will, too," came a small voice from the audience.

"What do you mean," Rowling laughed back. "Who's writing this book?"

Book four, whatever it's called, is due in July.

Landing such a hot literary commodity was something of a coup for Copperfield's and Readers Books in Sonoma, which collaborated on Rowling's appearance.

Tom Montan from Copperfield's said the two independent booksellers got behind the Harry Potter series early on and the publisher, Scholastic, appreciated and remembered that when the tour was scheduled earlier this year.

Standing behind Rowling while she signed books, a particularly muggle-like man in a black coat kept a sharp eye on doorways. (Muggles, for those who haven't read a Harry Potter book yet, are nonmagical, often humorless humans who have a hard time seeing the wonders of life around them.) The fellow in the dark coat wasn't looking for wonders. He was looking for trouble. Copperfield's and Readers had to hire security for Rowling, who has been bothered by a stalker recently.

Two Santa Rosa police officers hovered Friday night, partly in response to threats of protests by people who aren't enchanted by Rowling's positive portrayal of witchcraft. The books have generated some controversy in other parts of the country, but her appearances in Northern California have attracted nothing but fans. Lots of them.

"It's kind of sad but in this country, you aren't really a success as a writer unless somebody bans your books and you get threatened by a stalker," said a bookstore staffer manning a doorway. "So now you can say she's truly arrived."

For her fans, young and old -and the Santa Rosa audience was about half-and-half Friday night -Rowling's appearance was a bittersweet ride. After waiting in long lines to get into the gymnasium to hear Rowling read a short bit and say she wasn't giving any hints about what's going to happen in the fourth book, fans stood in another line to get her autograph.

Most left happy and fulfilled.

"These are absolutely the best books," said Michael Ballantyne, sitting on a curb in the not-verygood light from a streetlamp reading the second Harry Potter book for the fourth time.

He and his friend, Lucas Adams, both seventh-graders at San Jose Middle School in Novato, were waiting for friends to get through the autograph line.

"It was neat actually seeing her," Adams said, squinting at Rowling's big scrawled signature in his book.

For some who couldn't get in and others who expected something more, it was not a particularly good Floo trip.

"I just wanted to talk to her, that's all," said a teen-age girl in tears, after she was ushered quickly through the book signing line.

People came from Sacramento, Vallejo, Fort Bragg, Mendocino, Mill Valley, Novato as well as from Sonoma County.

Tickets, given free last month to the first 2,400 buyers of the third Harry Potter book at Copperfield's and Readers, were coveted items. Tickets for her appearance in the East Bay, also given free, were being scalped for money on the Internet.

Then there's the Case of The Weeping Widow who called Copperfield's with the sad story about a husband who just died and the three fatherless kids who stood in line to buy the books last month so they could get tickets to see the author and then, one day they were out on a boat at the lake with the books and tickets in a backpack that fell overboard and sunk to the bottom.

"Yes, I had my doubts but it was a pretty sad story and you want to be a trusting person," said Tom Montan at Copperfield's. "I sent her three tickets and then when I was at conference in the Bay Area with a bunch of other booksellers, we got to talking and it turned out she had called each of the stores in the Bay Area where Rowling was scheduled to speak. I don't know how many other tickets she got."