Remember when the stock market plummeted 1,000 points last year, taking trillions of dollars of market value with it, all because of a computer algorithm screw-up? How about Corzine and the MF Global debacle? Hackers breaking into government computer systems? Is it so far fetched to think that the entire US economy could be taken down just by gaming the system? Katonah resident James Othmer, writing under the pseudonym James Conway, takes on this cheery scenario in The Last Trade, a financial thriller just published by Dutton Books. Described by Publishers Weekly as “a compulsively readable look into the arcane world of high finance,” the book follows an evil hedge fund manager, a conflicted numbers guy, and an agent from the Terrorism and Financial Intelligence task force (who Publishers Weekly dubbed “the financial world equivalent of Lisbeth Salander”) from Hong Kong to Dubai to Manhattan, and Westchester’s own village of Katonah.