Scott Peterson's former mistress confesses in a book to be released this week that she "still thinks about Scott from time to time." She also confesses that "I sometimes wonder if he thinks about me."

The book by Amber Frey (search), "Witness For the Prosecution of Scott Peterson," is scheduled to be released Tuesday, but was mistakenly sold at a supermarket in the town of Modesto, where Peterson's wife, Laci, disappeared four months before her body was discovered in April 2003 along the San Francisco Bay shoreline.

Before the books were removed from shelves Saturday, the Modesto Bee obtained a copy.

The 214-page book, published by Regan Books, has chapter titles such as "Oh My God! Laci's baby is due on my birthday!" and "Isn't that a little twisted, Scott?"

Frey also writes that she had been afraid during the murder investigation, in which she played a key role by allowing police to tape her telephone calls with Scott Peterson (search).

An interview of Frey by NBC News' Matt Lauer was to be broadcast Tuesday on "Dateline," and portions of it were aired Monday on the "Today" show.

She told NBC that when she first called Modesto police, "I felt like I was going 100 miles per hour, just talking to this woman. She was taking my statement down."

Frey testified for six days in his six-month-long murder trial, during which prosecutors played hours of the taped calls. Though Peterson never implicated himself in the calls, they were central to the prosecution's case against him, portraying him as a callous liar who continued to carry on his affair even as police searched for his wife.

Peterson first told Frey he was unmarried, then claimed he had been married once but "lost" his wife.

She told NBC that she didn't ask him for details on losing his wife or why he hadn't mentioned it earlier.

"I didn't feel it was appropriate to pry on how, just because he was so emotional," she said. "It would have been like putting salt in the wound. He was sitting in front of me and he's, like, `You are not angry?' No, how can I be angry? I can understand."

About two weeks later on Christmas Eve 2002, the 27-year-old Laci Peterson (search) disappeared.

Her remains and those of her 8-month-old fetus were discovered not far from where Peterson claims to have been fishing alone the day his wife vanished.

He was convicted Nov. 12 on two counts of murder. On Dec. 13, the jury imposed the death penalty. Formal sentencing is set for Feb. 25.