This week's Southern California bestsellers are up on the Books page — and the holiday effect seems clear in at least one category. After Greg Mortenson's "Three Cups of Tea," the next four best-selling nonfiction trade paperbacks are all about food. Julia Child takes one slot, and two of the others are guides — including the locally published Eat: Los Angeles from Prospect Park Books. In hardcover, Sarah Palin and Edward M. Kennedy fell out of the top ten, and R. Crumb slides up to number one in nonfiction.