Forget the X Factor. For children’s books this month, it’s the S Factor that counts.

Coincidentally, publishers have just released new books from three old masters whose last names start with “S”—Dr. Seuss, Shel Silverstein, and Maurice Sendak. The new titles are making news because of their authors’ fame and age. Seuss died in 1991, Silverstein died in 1999, and Sendak is 83.

The timing makes sense. “It’s not surprising it would be fall season because it’s geared toward the holiday sales,” says book historian and critic Leonard S. Marcus. “And publishers love to publish things by well-known authors.” But ultimately, he says, sales will depend on “how good the books are.”

Silverstein’s Every Thing On It—released by HarperCollins on September 20—has taken an early lead. It got a one-week head start on Random House’s The Bippolo Seed and Other Lost Stories by Dr. Seuss. And booksellers like it. “I thought that one was just like the Shel Silverstein I know and love,” says Tegan Tigani, children’s book buyer and events coordinator for Queen Anne Books in Seattle. “Immediately I put a shelf talker on it.” Nielsen BookScan reports that for the week ending September 25, Every Thing On It sold 37,000 copies, and Maurice Sendak’s Bumble-Ardy sold 2400.

Bumble-Ardy, also published by HarperCollins, came out first, on September 6—but some librarians and booksellers believe the tale about a nine-year-old pig who throws a birthday party for himself is a bit dark for children and may appeal more to adult collectors.

Still, some booksellers are bullish on all three titles. At BookPeople in Austin, Tex., children’s book buyer Meghan Dietsche Goel says they are a “big deal.” BookPeople is displaying all three books face out in the front of the store. “So many readers are genuinely excited to see something new from them,” she says. “These things have been all over NPR, all kinds of media outlets. They’re coming in to see what the excitement is about.” Goel ordered about 100 copies of the Silverstein title and has sold more than half of them. She started with 40 copies of Bumble-Ardy and has just put another 20 on order since she is down to about eight. “I really liked it,” she says. “I really appreciate the dark humor of the book and thought it was kind of an outlandish romp.” With Dr. Seuss, she is starting by selling from the corrugated display.

In the Brooklyn Public Library system, each of the 60 branches is getting one copy of The Bippolo Seed and one copy of Every Thing On It. Only 35 of them are getting Bumble-Ardy. “Shel Silverstein is so popular,” says Francesca Burgess, children’s materials selector for BPL. “It was kind of a no-brainer. The same thing with the Dr. Seuss. Bumble-Ardy, even though it’s Sendak, it’s not like Where the Wild Things Are. It wouldn’t circulate well everywhere.”

Even before his new title came out, Dr. Seuss reigned supreme at the Brooklyn Public Library. Among authors of hardcover children’s fiction, he ranks first in terms of circulation. Sendak does not crack the top 100. Silverstein ranks #16 on a separate list of children’s nonfiction authors.

“Dr. Seuss books just sort of sell themselves still,” says Anne Cannon, a bookseller at King’s English Bookshop in Salt Lake City, Utah, and author of The Chihuahua Chase. “There’s so much affection for him. We have a shelf devoted just to Dr. Seuss. Out of the three, he’s the one that you don’t have to work very hard ever.”

Most of the librarians and booksellers PW spoke with have not yet read The Bippolo Seed, but they love Every Thing On It. “It’s kind of vintage and a lot of fun,” says Cannon. David Mowery, division chief of central youth services at the Brooklyn Public Library, agrees, calling it “wonderful.” He expects the other authors’ titles to do well, too. “They’re all popular authors who their other titles go out all the time,” he says.

Silverstein and Sendak got boosts from separate public radio stories on September 20 (Silverstein’s interview can be heard here, and Sendak’s here). “Our clients do tend to listen to NPR,” says Cannon. Other booksellers cite the NPR effect as well. “Once NPR stories hit, it seems to get huge,” says Tigani of Queen Anne Books.

Mary Taft, a bookseller at Prairie Lights in Iowa City, also mentions the radio segments. Prairie Lights, which initially ordered six copies and quickly got more, has already sold a dozen copies of Every Thing On It. The store ordered six copies of Sendak’s Bumble-Ardy but has not yet sold any of them. Prairie Lights is prominently displaying Silverstein’s poem collection “up with the new Brian Selznick [Wonderstruck],” Taft says. The only book with more buzz at Prairie Lights is Lightning Thief author Rick Riordan’s new one—The Son of Neptune (book #2 in the Heroes of Olympus series).

As Seuss scholar Charles Cohen notes in his introduction to The Bippolo Seed, a number of lost Geisel stories appeared in magazines from 1948 to 1959. He unearthed them by traveling to libraries and buying copies of the original publications. Geisel himself illustrated and wrote all seven “lost stories” in The Bippolo Seed. “I’m ripe for that one,” says Kenny Brechner, owner of DDG Booksellers in Farmington, Maine. “They were published works and interesting pieces of history, and the introduction by the Seuss scholar who found them is interesting to me.” He bought seven copies of The Bippolo Seed and has already sold five. He bought three copies of Every Thing On It and has sold one. He ordered five copies of Bumble-Ardy but has sold none of them so far. “I like it better than his last one [Mommy],” he says. “ [But] it lacks a certain spark that makes me think kids are going to love this book.”

Some librarians are being cautious. Maeve Visser Knoth, youth services librarian for the San Mateo County Library in Atherton, Calif., who buys for 12 libraries and a bookmobile, is buying just a few copies of the Seuss and Silverstein books for her bigger libraries and just one for the smaller ones. She is holding out on the Sendak book until she sees it. “The later Maurice Sendak is not what you give to kids,” she says. “You give those to collectors. There are adults who will be interested, but I would rather have five clean copies of Where the Wild Things Are and not really worry about his most recent stuff.” She would use his new title in the graduate classes when she teaches graduate classes on children’s literature.

Like many librarians, Knoth cautions that it’s best to avoid “jumping to conclusions that everything will be good just because it’s from a big name.” Not so. “You look and you say, ‘That person’s won the Newbery, so this next book must be good.’ That’s not always true.”

Knoth hasn’t yet seen the new Seuss, so she is reserving judgment about another posthumous book by the author. Take Hooray for Diffendoofer Day! It was published in 1998, seven years after Dr. Seuss’s death, with, as the jacket notes, “some help from Jack Prelutsky and Lane Smith.” “No one would put it in the Seuss canon,” she says. But the new book is written and illustrated by Theodor Geisel himself.

So far historian Marcus has only read the Sendak book. “Anything he does is always very interesting,” he says. “It’s just like seeing another aspect about his feelings about childhood. The art is strange and festive at the same time. It’s a little Dickensian.”

Like Knoth, Marcus notes the spotty history of posthumous Seuss publications. “That book Daisy-Head Mayzie was pretty awful,” he says. (Theodor Geisel did not illustrate the book, which came out four years after his death.) “In general, these things are done for the obvious reasons, for commercial reasons, and what they call ‘extending the brand.’ ”

And Marcus find it heartening that Sendak—and next month, Eric Carle with The Artist Who Painted a Blue Horse—are still coming out with new books in their 80s. “I just think that’s wonderful,” he says.