Forget blackmail and junkets—according to the growing body of literature about “Page Six” (four books this year), it’s full-on debauchery that fuels the Post’s gossip flagship. Particularly at Siberia, a dive across from the Port Authority. “Page Six” freelancer Tom Sykes (Plum’s brother) opens his upcoming memoir, What Did I Do Last Night?, with him destroying a Pac-Man machine at Siberia, and goes on to chronicle his night-crawling. “At some point,” he writes, “someone—sometimes me—would say, ‘Want to get some blow?’ ” Drinking buddy and current “Six”-er Chris Wilson is quoted as saying, “You couldn’t do this job if you were sober.” So it goes, too, in ex-“Six”-er Ian Spiegelman’s thriller à clef, Welcome to Yesterday, where “Charlie Gaines” (a fictionalized Jared Paul Stern) Maces a bodyguard outside a party and boasts, “They don’t put their hands on us. They’re just touring through—we live here.” Well, maybe not—following an anti–News Corp. rant by Spiegelman, “Page Six” staffers were conspicuously absent from his book party at Marquee (with an after-party you-know-where). Next: Is the Gristedes Guy Mayor-like?