Amanda Knox book deal to pay back parents?

Amanda Knox was freed from an Italian prison in October, after the Seattle college student was cleared of murder charges.

But that was not the end of her story.

Knox just signed a book deal with publisher HarperCollins worth millions. It has been reported the deal is worth $4 million.

"48 Hours: Mystery" correspondent Peter Van Sant, who has been covering her case since Knox's first trial in 2008, said that Knox may have agreed to write the book because to repay her parents for their long fight to free her.

Pictures: Amanda Knox not guilty of murder

"Amanda's best friend had told us that she was always hoping one day to be able to repay the sacrifice that her parents put out there to save her and get her out of jail," Van Sant said.

He also said, "I was told there was more interest in Amanda Knox's story than in Bill Clinton and Hillary Clinton's books. The bidding was fierce. The figure I've been told $4 million is a little high. But it is a seven-figure advance, and good for her. The family was more than a million dollars in debt from all of this."

Knox, 24, was acquitted of murder charges in Perugia, Italy this past October after initially being convicted of killing her British roommate, Meredith Kercher, in 2009. The former exchange student has not publicly discussed her ordeal beyond a brief expression of gratitude upon her release last October. The book is expected to come out in early 2013.

The book, Van Sant said, is likely to focus on the journal she kept during her four years in prison.

"I've been told that there are all sorts of stories of her experience behind bars that she has never shared," Van Sant said. "In fact, when they met with these seven publishers, I was told by a source at that meeting that there wasn't a dry eye in the place. So she has some very powerful stories to tell.

"Keep in mind, we've been reporting the story for four years," Van Sant said. "... CBS News was the first to say she was wrongly accused and wrongly convicted. This was an absolutely innocent young honor student from Seattle who went through an experience she did not deserve. I think her story will be fascinating."

Amanda Knox signs book deal with HarperCollins

Amanda Knox memoir scheduled for 2013

This week Italian prosecutors challenged the acquittal of Knox and her ex-boyfriend, asking that the conviction from the first trial be reinstated. However, the paper review is believed will go nowhere unless a major procedural error is detected, Van Sant said.

Amanda Knox acquittal on appeal challenged by Italian prosecutors

Pictures: Amanda Knox Personal Photos

For more on Amanda Knox's book and ongoing case, watch the video in the player above for Van Sant's full discussion on "CBS This Morning."