Nicolas Cage struck gold at the top of the U.S. box office at the weekend with his National Treasure sequel BOOK OF SECRETS. The movie star's latest outing as historian adventurer Ben Gates opened with $45.5 million (GBP22.7 million) - more than the combined totals of four other newly-released pre-Christmas (07) blockbusters. Will Smith's sci-fi movie I Am Legend, which broke December box office records last week, slipped from one to two with an impressive $34.2 million (GBP17.1 million) second-weekend take. That film's 10-day tally rises to a staggering $137.5 million (GBP68.75). Family film Alvin and the Chipmunks dropped a spot to three, while new releases Charlie Wilson's War and Sweeney Todd entered the Christmas box office chart at four and five respectively.