ST. CHARLES — The discovery in an Arnold basement of more than 3,000 well-preserved old comic books, including a copy of Spider-Man's first appearance in print, has a small but passionate world of collectors abuzz.

The books are to be sold at auction Sunday and Monday in a ballroom at the Ameristar Casino in St. Charles. The auction company will make them available for viewing today and Saturday at the same place.

"The interest has been amazing," said Tina Weiman of Hazelwood, co-owner of Mound City Auctions. "All the phone calls, the chat-room talk. People flying in from New York. We do a lot of auctions, but this has become a whole different ballgame."

Weiman said the comic books, mainly from the 1960s, were found in the basement of a home in Arnold that her company was hired to dispose of at auction. She said a man who died several years ago had collected them as a boy growing up in south St. Louis County, then packed them away. After his mother died earlier this year, a cousin who became heir to the estate found the comic books.

The heir wants to remain anonymous, Weiman said. She recommended setting up a separate auction for the comic books. A short time later, she said, a collector called and offered to buy all of them for $50,000.

"When that happens, you add another zero to get closer to the real value," Weiman said. She predicted that sale of all the magazines will bring in more than $500,000.

Weiman said she and her business-partner husband, Rob, took the comic books to Sarasota, Fla., which is home to a place called the Comic Book Grading Corp. That company formally rated about 1,000 of the most valuable books in the Arnold discovery.

Weiman said the hottest book, issue No. 15 of Amazing Fantasy — the one introducing Spider-Man — could go for more than the $65,000 sale of the split-level home in which it was found.

Two other examples of hot books on the auction block are the 22nd issue of Showcase, which included the first appearance of Silver Age Green Lantern, and a near pristine copy of the first issue of X-Men.

Mark Farace, owner of All-American Collectibles in the St. Louis Hills neighborhood, called the discovery an important one, if not unprecedented. He said the 1960s were part of what's known as the "silver age" for comics, with the "golden age" generally dating to the 1940s. The likes of Superman and Batman made their debuts in the late 1930s, and quality copies of their first appearances can go for more than $300,000.

"Still, this is a pretty big deal," Farace said. "I've owned this shop for 11 years, and I can only remember two other times like this. Most people already have dug into their closets and basements and sold their good stuff."

Farace said he planned to attend, partly to observe whether collectors go heavy on buying or sit back and assess the market. "There will be a lot of folks in from out of town," he said. "I know a lot of collectors who figure they won't be able to afford much. But there will be a big crowd."

Weiman said viewing will begin this morning after she and Rob are able to prepare comics for display. The auction, both live and online, is to begin at 10 a.m. Sunday and Monday, with the most valuable books divided equally between both days.

She said this will be their company's first auction of comic books. "But we have done collectibles before," Weiman said. "I understand people's passions. Think about baseball card collectors. And from what I've seen so far, comic book people take the cake."