First-time novelist Macdonald delivers twists and turns with the ease of an old pro in this brainy, exotic suspense thriller. Oxford undergraduate Ben Ashurst is smart but impressionable, and this reputation earns him the opportunity to be a guinea pig in a study his biology professor is directing, funded by a multinational drug company. If Ben and his beautiful new girlfriend, Cara, agree to have tiny experimental emotion-sensors sewed to the back of their heads, they'll be sent on a free beach-resort vacation in Kenya, designed to stimulate their emotions and thoroughly test the sensors. For the first few days, the vacation is all Ben had hoped for. But then a case of food-poisoning, suspicions about Cara, incarceration in the local jail and a possible drug-trafficking frameup make Ben wonder what is going on. It becomes clear that he has not been let in on the full nature of the experiment, and he begins to question who is actually behind it. Tangled in a web of deception, Ben watches as his life falls apart around him, but refuses to go down quietly. Right up to the very end, we are kept guessing: how high are the stakes of the experiment? And who among Ben's friends is involved? Macdonald, a 27-year-old Oxford graduate born in Nairobi, Kenya, convincingly depicts Ben's cliquish, upper-crust partying at Oxford and hedonistic African adventuring. The novel's maze-like plot may take a few turns too many, but straightforward prose and a well-developed protagonist buoy this promising first effort. (Mar.) Forecast: A touch of intellectual macabre, la Secret History, gives this thriller a sexy twist. With foreign rights already sold in 14 countries, film rights sold to Heyday Film and a five-city author tour in the offing, the book is poised to score.