PLANNED: Laci Peterson’s mother, Sharon Rocha, is writing a book about her slain daughter, with a December publishing date in place. Titled Laci and scheduled to be priced at $25.95, Rocha’s book is listed on the Web site of Crown Publishing, a division of Random House. Ron Grantski, Laci Peterson’s stepfather, tells the Modesto Bee that he would help Rocha, his longtime companion, write the book. “A lot of truths haven’t been told, and I kind of think they should be,” he said. “Everyone has written little bits and pieces.