Ever since the appearance of Thomas Pynchon's epic, mind-bending Gravity's Rainbow (1973), rumors have circulated among the faithful that the elusive author was working on two new projects: a novel about Japanese monster movies and one dealing with the 18th century drawing of the Mason-Dixon line between the (then) colonies of Pennsylvania and Maryland. Fragments of a Godzilla-like episode indeed appeared in Pynchon's Vineland (1990), and now here comes a real monster: Mason & Dixon (Henry Holt; 773 pages; $27.50).
Pynchon, the one-time enfant terrible of American literature, turns 60 this May. He still refuses to give interviews or pose for...