Joan Rivers' saved her best material for last.

At least that's what a source is saying. The comedienne reportedly requested for a book to be published after her death.

"Joan requested that after she is gone, her personal diaries be turned into a book," a source said. "The problem is, they are having a hard time shopping it around because of how over-the-top defamatory it is."

Perhaps the book will touch on Jay Leno, who never invited her onto "The Tonight Show."

Leno recently explained that he didn't invite Rivers onto the show out of respect for Johnny Carson, who had a falling out with Rivers. He said that after Carson's death it became awkward, and Rivers continued to talk about it.

But Leno doesn't regret it, and he had no hard feelings toward Rivers. He even said that Rivers was the first autograph he had gotten.

Howard Stern, however, didn't think Leno's answer was good enough.

"Jay Leno is a f*cking phony," Stern said. "He's a liar. That's not an honest answer. Jay didn't even thank Johnny on the first night of 'The Tonight Show.' Remember that was a big controversy?"

Recently, about 40 people who worked on "The Joan Rivers Show" gathered in New York from all over the world to honor Rivers, notes PageSix.

For many, it was the first time seeing each other since her show went off the air in 1993.

"There were tears and laughter in the room," according to the site. "Everybody lamented getting older and wiser but [noted] Joan had been looking younger and more relevant than ever."

There was also a group who gathered in Los Angeles at the same time as those in New York.