Sarah Palin’s sudden announcement that she will resign as Alaska’s governor has thrown unforeseen risk into the already uncertain market for books about her — and by her. Earlier this year, Palin inked a deal with HarperCollins for her memoir, due out in spring 2010. Washington lawyer Robert B. Barnett helped her secure an advance that has been reported to be several million dollars. The actual sales of her story, however, will depend entirely on how she plays her next hand. “If she has an eye on 2012, she probably will write a carefully worded, bland policy book that won’t...