It's like Madame Bovary, except that in Northanger Abbey, reading fiction isn't a fatal affliction. It doesn't ruin women for life. It does incline the main character to flights of fancy, but she remains rooted in the real world and in real emotion.
Northanger Abbey is, says the commentary in the book, one of the most accessible of Jane Austen's works. I'd have to agree. It is much livelier than her other works (which is not to say that I don't like her other books, because I do.) But Northanger Abbey has an energy and drive to it that mirrors the main character, and this gives the whole book and writing style a different feel from her other books.
Catherine, a sheltered young woman, goes with family friends to Bath, where she falls in with Isabella and John Morland, both of whom passionately declare their affection for her, whether she wants it or not. (In one case she does, in the other case she doesn't.) This extravagance of affection is likewise bestowed upon her brother.
But Catherine liked one man exceedingly before having met the Morlands (and why, exactly, is probably one of the weaker parts of the book), and she dodges social scandal, misrepresentation of her desires and means, and her own overly vivid imagination in forging relationships worth having.
It's a bit clunky at times in terms of plot, but more than makes up for it in terms of energy.