Scott Peterson (search) remains cheerful despite being sentenced to death just days ago, buoyed in part by the constant flow of fan mail he continues to receive, the San Mateo County sheriff said Thursday.

Peterson's demeanor hasn't changed since he was transferred months ago from Stanislaus County to the San Mateo County Jail, even after jurors found him guilty of two counts of murder, Sheriff Don Horsley said during a news conference. On Monday, the jury recommended he be sent to California's death row.

"He has been his normal self. He is very cheerful. He is very compliant and very helpful," Horsley said, adding that jailers describe him as a model prisoner.

"When we move him from one area to the next, they do have to put restraints on him and he helps them," Horsley said. "He's not suicidal."

He added, however, that Peterson has lost "a lot of weight."

"I told him ... 'Scott, you've lost weight. Is the food bad?"' Horsley said. "He said, `No, it's actually better than in Stanislaus County."'

Peterson was convicted Nov. 12 of murdering his eight-months-pregnant wife, Laci, and the fetus she was carrying.

Prosecutors said he killed his wife on or around Christmas Eve 2002 and dumped her weighted body into San Francisco Bay (search). Her remains and those of the fetus were discovered about four months later, not far from where Peterson claims to have gone fishing alone the morning his wife vanished.

His case was moved from Stanislaus County, where the Petersons lived in Laci's hometown of Modesto, after a judge found he couldn't get a fair trial there.

While he awaits formal sentencing in February, Peterson is staying in a 10-foot-by-10-foot cell in the county jail. Guards let him out of his cell twice a day for an hour to exercise alone in the yard, watch television or use a computer without Internet access.

Horsley said Peterson receives visits from family members every three to five days.

"He gets a lot of mail," the sheriff said. "He does have a fan club."

Meanwhile, Regan Books announced Thursday it had signed a deal with Peterson's mistress, Amber Frey (search). The book is due to go on sale Jan. 4.

"I am very gratified that Regan Books has agreed to publish Amber's story," said Frey's attorney, Gloria Allred. "We think her story of courage in crisis will inspire others who have been betrayed to fight back for truth and justice."

With the publication date less than three weeks away, Frey will either have to write the book in record time or has already been working on it.

Allred declined comment Thursday when asked by The Associated Press how far along Frey was with the manuscript and whether she would receive help writing it.