London film producer David Heyman may not appear to have much in common with Hollywood legend David O. Selznick.But Heyman, who paid a mere $500,000 to option “Harry Potter” for Warner Bros. in 1997, is suddenly a force in Hollywood. As the Harry Potter franchise begins cartwheeling through AOL Time Warner’s distribution channels, Heyman’s deal for the book could go down in history as one of the most important lit acquisitions since Selznick paid $50,000 for rights to “Gone With the Wind.” Analysts are speculating that Harry’s global BO, merchandise, TV and other spinoffs could create billions of dollars in revenues for the conglom. Heyman and his development director, Tanya Seghatchian, had the prescience to buy the first Harry Potter book, with an option on the subsequent volumes, even before they’d been published Stateside. It was the first property Heyman optioned under his production banner, Heyday Films. The company has a deal with Warner Bros., but remains based in London. Heyman is the son of financier John Heyman and producer Norma Heyman. After 17 years living Stateside, he says — including years at Warner Bros. and UA — “I really believed I could make films not just for the British but for the American and European audience.” Heyday has since optioned other literary material, including Robyn Sisman’s romantic comedy, “Just Friends,” Darren Chan’s kids book “Cirque du Freak,” which comes with an endorsement from Potter creator J.K. Rowling, and the Patricia Highsmith novel, “Suspension of Mercy.” TODAY MARKS Phyllis Grann’s final day as CEO of Penguin Putnam, one of the top jobs in publishing. Grann hasn’t disclosed her next move, but if there’s any truth to the rumors sweeping the industry, it could hit like an earthquake, redrawing the balance of power in a business already rattled by key defections by editors and authors. Grann helped build Putnam into a commercial powerhouse, publishing such writers as Tom Clancy, Patricia Cornwall, Robin Cook, Nora Roberts and Dick Francis. If several exit with Grann, Putnam would be left reeling. But it’s hard to say whether that will happen. Putnam wouldn’t confirm whether there was a non-compete clause in Grann’s contract. Some of her authors could have signed key personel clauses, allowing them to follow her elsewhere. But Trident Media Group head Robert Gottlieb says that could prove detrimental to books orphaned at Putnam under multi-book contracts. “Those books would be published by a publisher who no longer has a future with the authors,” he says. “Whether it’s a first novelist or a bestseller, leaving books behind is always risky.” It’s long been rumored that Grann may have already negotiated a contract at another house. Most sources have her moving to the Random House imprint of Random, Inc., perhaps as a sort of editor at large. She’s also said to have talked to HarperCollins chief Jane Friedman and top Simon & Schuster exec John Newcomb about launching her own imprint. Random House spokeman Stuart Applebaum said Tuesday no announcement about Grann was forthcoming. Virtually any job in the industry would mean a reduction in responsibilities for Grann. As the boss of Penguin Putnam’s highly centralized and multifaceted publishing operations, it could be hard to adjust to running an imprint, especially at a highly decentralized company like Random, Inc. Then again that’s the path former Penguin topper Peter Mayer took when he stepped down a few years back and assumed the reins of the Overlook Press. DIRECTOR STEVEN MARTIN, whose documentary about Russian inventor Leon Theremin won the 1994 Sundance Filmmaker’s Trophy, is adapting William Kotzwinkle’s 1974 novel, “The Fan Man.” Martin will direct the project for the international film, TV and new media company Radical Media. Theremin was kidnapped by Soviet agents after his electronic instrument, the theremin, whose eerie whistling sound is best known today from campy scifi and suspense scores, became a sensation on the international stage. Martin is now adapting the docu as a feature for Milos Forman. Kotzwinkle has resisted other bids to option the novel, a cult classic about the ’60s counterculture, says ICM’s Ron Bernstein. But he was charmed by Martin’s documentary. When Martin visited Kotzwinkle in Maine, he brought a theramin for a jam session with the author. “Fan Man” depicts the misadventures of a Manhattan bohemian named Horse Badorties who shambles around the Lower East Side trying to put together a huge outdoor concert. Radical Media is now shopping the project to financiers and cast. The author is repped by Bernstein and Henry Dunow.