You don’t see many cads in the wild any more: they are, perhaps, an extinct species. This staple of the 19th-century novel is a rare figure in mainstream literature these days. Undoubtedly if I looked hard enough, I would find a subculture of spicy contemporary rogues – tweet me your picks – but in this instance I am concerned with the noxious products of class and odiously outdated sexual politics that make me thankful to live in an age where I can get a credit card without my husband’s permission. Dangerously handsome young men with more money than sense, often...