Fittingly for a satire, Thackeray writes Vanity Fair with a sarcastic and snarky mood—by the narrator's opening description of the fair itself, this is "not a moral place certainly; nor a merry one, though very noisy." A similar strain of frank sarcasm carries through to the very last page.
While much of the novel is delightful for the sheer entertainment value of Thackeray's brilliant deconstruction of the English upper class, he does not pull his punches—the satire can get quite pointed and even almost brutal, as when he describes Becky as a vicious siren out of Greek myth in Chapter 64:
In describing this siren, singing and smiling, coaxing and cajoling, the author, with modest pride, asks his readers all round, has he once forgotten the laws of politeness, and showed the monster’s hideous tail above water? No! Those who like may peep down under waves that are pretty transparent, and see it writhing and twirling, diabolically hideous and slimy, flapping amongst bones, or curling round corpses;
This passage contains a little bit of every major mood in the novel: Thackeray is being playful and self-aggrandizing about how well he has characterized Becky, lightening the mood of the situation while immediately thereafter diving in and describing the horrific nature of Becky's character in lurid detail—and thereby darkening it again.
