Unsurprisingly, given his background as a screenwriter, Patrick deWitt’s novels owe as much to cinematic sources as they do to literary ones. The Booker-shortlisted The Sisters Brothers (2011), a darkly comic Western narrated by a conscience-stricken assassin, is the sort of riff on Cormac McCarthy you might expect from the Coen Brothers. Undermajordomo Minor (2015), set in the forested depths of a vaguely sketched Mitteleuropa, recalled The Grand Budapest Hotel. Now comes deWitt’s screwball comedy in the form of his fourth novel, French Exit, a Preston Sturges-esque satire on New York’s moneyed classes and the casual brutality of their emotional lives, with more than a whiff of The Royal Tenenbaums…