The gray Scottish fold died Saturday of kidney failure, said Peter Gethers, Norton's owner and author of "The Cat Who Went to Paris" and "A Cat Abroad."
"For me, he's irreplaceable," Gethers said Wednesday. "Everyone's just so sad because they felt through the books that they knew him."
Gethers, a reformed cat-hater, said he had no idea how to treat Norton when he received the pet as a gift from an ex-girlfriend. "So I treated him like a dog. I took him with me everywhere," Gethers said.
Norton flew on the Concorde, stayed in a hotel with view of the Parisian skyline and attended meetings with director Roman Polanski and actor Harrison Ford.
An editor-friend encouraged Gether to write about Norton's adventures.
"The Cat Who Went to Paris," published by Fawcett Books, tells how Norton and Gethers became traveling companions. It also tells how human and feline win the love of fair Janis, a woman who moves in with the pair.
The second book, "A Cat Abroad," picks up with the trio traveling to the French Riviera, Spain and Italy, and the perks of a U.S. book tour, including a launch party at the trendy restaurant Spago in Los Angeles.
Gethers was writing a third installment, "The Cat Who Will Live Forever," when Norton died.
"I wasn't expecting this to happen when I made the deal. It changes things a bit," he said.
The book is expected to be completed in about a year.
By Chelsea J. Carter