Jennifer Wilson in the LA Review of Books [h/t: Tunku Varadarajan]:
The question of miscegenation would not appear in Nabokov’s work until some 13 years later, with the scandalous 1955 publication of Lolita — a novel Nabokov knew was a “timebomb,” as he wrote to an American friend. In “On a Book Entitled Lolita,” Nabokov writes that there are only three subjects American publishers find taboo: pedophilia, atheism (which carried connotations of “godless” communism), and “a Negro-White marriage which is a complete and glorious success resulting in lots of children and grandchildren.” This invocation of American hysteria surrounding miscegenation seems jarring at first. After all, Lolita is concerned with actual sexual perversity, not what racist distortion falsely presents as sexual perversity. But a closer reading demonstrates just how central the theme of American racism is to Nabokov’s narrative.
Early on in Lolita, Humbert Humbert learns that his first wife, Valeria, relocated from Europe to the United States, where she became a subject of an ethnological experiment. The project involved research on “human and racial reactions to a diet of bananas and dates”; this vignette is emblematic of the United States’s obsession with understanding race through “science,” and is tinged with overtones of Nazi eugenicist experimentation. A forgotten target of Nabokov’s satirical eye, the United States’s obsession with racial purity and the policing sex almost exclusively toward that end, is arguably a subplot of Lolita.
Indeed, one could argue that part of why Humbert Humbert so successfully evades discovery as he takes Lolita from motel to motel is that white men, even white pedophiles, were not surveilled with the same force or regularity as black men engaged in the “sex crime” of miscegenation. The Mann Act, which made transporting girls and women across state lines for the purpose of “debauchery” illegal, looms in the background of Lolita.