Manil Suri was deep into writing his latest novel, “The City of Devi,” when he realized something alarming: the novel was impossible to finish. The mathematics professor even used a mathematical construct, a possibility tree, to arrive at his conclusion.  He described the process of creating this mathematical “proof” in an essay for “The Daily Beast.” Of course, Suri did eventually finish the novel, which was published earlier this year. Despite the fact that he disproved his own proof, Suri feels that his mathematical conclusion was a worthwhile endeavor, because it allowed him to reach the insights he needed about …