Austen keeps the mood of Lady Susan light and humorous, giving readers space to enjoy the foibles and social drama of Lady Susan's various entanglements. On a surface level, this lighter mood remains fairly consistent throughout the novel. Underlying this humor, however, are the realities of the characters' situations: Frederica, for instance, finds herself with a relatively self-absorbed and uncaring mother. Her circumstances, though they improve, start out as bleak indeed—in direct contrast to the general mood of the novel. This approach to mood is characteristic of Austen's writing: the dry wit and satire she imbues through tone establishes a humorous baseline for the novel, remaining throughout; and later, when the stakes are higher, this humorous mood contrasts with the often quite serious or dire circumstances of Austen's characters.
Such an approach to mood is common for satirical novels—indeed, Austen is often considered one of the most prominent and cutting satirists of her time, laying bare the foibles of British society with impunity. What other satirists miss out on, however, is the sense of impish delight Austen exhibits with her humorous mood and scathing tone. She has the unique ability to make readers feel complicit in jokes made at the expense of rude and ridiculous people.