Ambitious, erudite and well-sourced, Leavitt’s 12th work of fiction centers on the relationship between mathematicians G.H. Hardy (1877–1947) and Srinivasa Ramanujan (1887–1920). In January of 1913, Cambridge-based Hardy receives a nine-page letter filled with prime number theorems from S. Ramanujan, a young accounts clerk in Madras. Intrigued, Hardy consults his colleague and collaborator, J.E. Littlewood; the two soon decide Ramanujan is a mathematical genius and that he should emigrate to Cambridge to work with them. Hardy recruits the young, eager don, Eric Neville, and his wife, Alice, to travel to India and expedite Ramanujan’s arrival; Alice’s changing affections, WWI and Ramanujan’s enigmatic ailments add obstacles. Meanwhile, Hardy, a reclusive scholar and closeted homosexual, narrates a second story line cast as a series of 1936 Harvard lectures, some of them imagined. Ramanujan comes to renown as the “the Hindu calculator”; discussions of mathematics and bits of Cambridge’s often risqué academic culture (including D.H. Lawrence’s 1915 visit) add authenticity. Hardy is hardly likable, however, and Leavitt (While England Sleeps, etc.) packs too much into the epic-length proceedings, at the expense of pace. (Sept.)