I recently read, Barnaby Rudge, one of Dickens' less celebrated novels. It's set in 1780, during the Gordon riots, a period of civil unrest I'd never heard of before, stirred up by Protestant rabble rousers enraged by legislation that eased some of the restrictions on Britain's Catholics. I can see why the book might strike some as unsatisfying; the bad guy is a crafty flatterer who persuades the addled Lord Gordon to act as a leader, but it's not especially clear what his motives are, besides causing trouble.
Nevertheless, the descriptions of the riots are fabulous and terrifying depictions of mob violence. In one scene, an offshoot of the mobs burns down the stately home of a prominent Catholic, and one rioter is so drunk that he passes out with his mouth open, whereupon the fire melts the lead in the window glass until it pours down the wall, into this guy's mouth, killing him. Eek! That's an image I won't soon forget.
One interesting theme of the book is the conflict between 19th-century Victorian middle-class moral attitudes and the sophistication of the 18th century. The wickedness of another bad guy in the novel, Sir John Chester, is made manifest in his exquisite and amiable manners. He's evil because he's insincere, smooth and calculating. His idol is Philip Stanhope, the Earl of Chesterfield, famous for writing a series of letters to his son offering advice on how to be a man of the world. I remember reading these in college; like Machiavelli's The Prince and Castiglione's The Courtier, they recommend dissembling and manipulation, hallmarks of Sir John's behavior.
To the Victorians, this sort of slickness was an example of why the decadent aristocracy needed to surrender power to the morally upright middle class. Sir John's son, Edward, demonstrates his readiness for the new dispensation by rejecting his father's plans for him (marrying money) and betrothing himself to a modest Catholic girl of decent family but no serious fortune. The problem for the novelist is that the wily and unflappable Sir John is a lot more fun to read about than good old Edward, who's a bit of a stiff.
Dickens is a perpetual reminder of something novelists tend to forget: great villains can more than make up for uninteresting heroes.