When reading this novel, don't you often get the feeling that you're floating way above the action and looking down on a bunch of little ants scurrying around? That right there demonstrates how the narrator's tone functions. Dickens often uses the trick of distancing readers from the characters and the plot. For instance, let's look at this description of Bounderby talking to Mrs. Gradgrind, in Book 1, Chapter 4:
[Bounderby] stood before the fire, partly because it was a cool spring afternoon…partly because he thus took up a commanding position, from which to subdue Mrs. Gradgrind[…]
Mrs. Gradgrind, a little, thin, white, pink-eyed bundle of shawls, of surpassing feebleness, mental and bodily; who was always taking physic without any effect, and who, whenever she showed a symptom of coming to life, was invariably stunned by some weighty piece of fact tumbling on her[…]
'For years, ma'am, I was one of the most miserable little wretches ever seen. I was so sickly, that I was always moaning and groaning. I was so ragged and dirty, that you wouldn't have touched me with a pair of tongs.'
Mrs. Gradgrind faintly looked at the tongs, as the most appropriate thing her imbecility could think of doing. (1.4.5-11)
Here, it's the narrator's voice that tells us with unquestioned authority what to make of these two people. Bounderby? Well, his M.O. is to dominate the weak – check out how even his standing in front of the fireplace is meant to "subdue" the already pretty subdued Mrs. Gradgrind. Think about the way the narrator inserts that line, when just a simple journalistic reporting would say "Bounderby stood before the fire" without trying to attribute motivations.
Not that Mrs. Gradgrind gets off easy, either, what with those savagely mocking "feeble of mind" and "imbecile" comments. It's a tricky moment here – on the one hand, we're meant to dislike Bounderby for being such a bully. But on the other hand, the narrator kind of does the same exact thing by picking on the fairly defenseless Mrs. Gradgrind. How do we resolve this? How do we react to the narrator sarcastically picking apart the characters? Does the narrator's authority give him more right to domineer over the characters?