When is a joke not a joke? What's the boundary between reality and performance? Can something that seems simply embarrassing at first eventually become funny? Or even, dare we say it, sublime? Can comedy be used to help us understand the limits of our understanding of reality?

These kinds of questions, probed deeply by comedian Andy Kaufman and his critics and fans, are not ones Chris Elliott is answering in The Guy Under the Sheets: The Unauthorized Autobiography, just released in paperback. Elliott does, however, allege that Kaufman sent him death threats for ripping off his act. And that he made it onto David Letterman's show by throwing up on command for him on the observation deck at 30 Rockefeller Center. Elliott says he was a tour guide there, selling tickets for the deck, and he'd skim the profits on behalf of gangster John Gotti. He also says that his parents were Bette Davis and Sam Elliott, that he was the model for Andy Warhol's first soup can painting, and that he hung out with Marlon Brando on a desert island.

The whoppers keep coming with Elliott's signature bombastic goofiness. As a boy, he took advice from an "old black Con Edison man, who would pop up from under the street through various manholes." A little later, he lived with his relatives, the Edies of Grey Gardens fame, even though "it has proven difficult to determine exactly how they were related to Chris." This understatement of the difficulty of proof in a book that is cover-to-cover lies is one of the things that makes it so funny. He recalls introducing himself by knocking on one Edie's head because he thought it was the door, presenting her with a gift of melted vanilla ice cream. Upon receiving it, she marches "back and forth waving a little American flag."

Despite its absurdity, the book also seems to contain a confessional aspect, with Elliott revealing germs of doubt about his own abilities as a comedian, or his questionable film career. Exaggerated bits about childhood hysterical blindness and speech impediments might be fake, but a reader gets the sense that Elliott is trying to capture the feel of his awkward youth.

Once he broke into entertainment, he probably didn't light Lauren Bacall's fingers on fire at the debut of his sitcom Get a Life, and Tom Hanks probably didn't steal the idea for Castaway from him, but Elliott probably has felt like an outsider for much of his career. The women he chooses for himself in his book -- sexpert Dr. Ruth, serial killer Aileen Wournos, and Harold and Maude actress Ruth Gordon -- might say something about his sexual self-image.

Elliott gives himself some victories, too, like his claim to having been interviewed by TV legend Mike Wallace, albeit after breaking into his home and demanding a chat at knife-point. He was even invited onstage by Elton John at Madison Square Garden, only to realize the standing ovation he gets is due to a squirrel running under the seats. Even the stupidest made-up moments have these little twists that make what at first seems ridiculous feel a little bit real. It would be pushing it to say there's a melancholy undertone to this wacky fake memoir, that Elliott somehow manages to write a book full of lies that builds to the truth. Or would it? Did he do that on purpose? If this book is entirely a joke, on whom is the joke being played? Maybe, like Kaufman, Elliott is probing these bigger ideas in The Guy Under the Sheets after all. Or maybe I'm just pulling your leg.