Fans of the reclusive postmodernist author Thomas Pynchon were presented with a puzzle last week: A description, purportedly by the author himself, of Mr.Pynchon’s untitled forthcoming novel — his first since 1997’s “Mason & Dixon” — appeared briefly on Amazon, then disappeared. Followers of Mr. Pynchon’s pointed this out on Amazon immediately, and the blog Pynchonoid reported on the mysterious disappearance.

In an e-mail, a spokesman for Amazon, Sean Sundwall, said the description was indeed by the author and that it was taken down at the request of the publisher, Penguin Press, because “the date when they wanted to make the book description available changed.” If that was the case, the attention the glitch attracted made them change their minds; the description was back up on Amazon by Friday. Mr. Sundwall also disclosed the title: “Against the Day.” Calls to Penguin Press and to Mr. Pynchon’s agent, Melanie Jackson, went unreturned.

Penguin Press will publish the novel, which runs to 992 pages — even longer than Mr. Pynchon’s previous doorstop of a novel, “Gravity’s Rainbow” — on December 5.

The description says the plot takes place “between the Chicago World’s Fair of 1893 and the years just after World War I … [moving] from the labor troubles in Colorado to turn-of-the-century New York, to London and Gottingen, Venice and Vienna, the Balkans, Central Asia, Siberia at the time of the mysterious Tunguska Event, Mexico during the Revolution, postwar Paris, silent-era Hollywood, and one or two places not strictly speaking on the map at all.” As for the sometimes surreal proceedings, Mr. Pynchon writes: “If it is not the world, it is what the world might be with a minor adjustment or two. According to some, this is one of the main purposes of fiction. Let the reader decide, let the reader beware. Good luck.”