The narrative tone in Nicholas Nickleby is some combination of didactic, analytical, philosophical, and satirical. Dickens himself appears to speak through the voice of the narrator at times, pontificating about social issues or analyzing his own characters. Note the following example from Chapter 28, in which the narrator reflects on Sir Mulberry's pursuit of Kate:
The reflections of Sir Mulberry Hawk turned upon Kate Nickleby, and were, in brief, that she was undoubtedly handsome; [and that the pursuit of her would greatly] enhance his reputation with the world. And lest this last consideration—no mean or secondary one with Sir Mulberry—should sound strangely in the ears of some, let it be remembered that most men live in a world of their own, and that in that limited circle alone are they ambitious for distinction and applause. Sir Mulberry's world was peopled with profligates, and he acted accordingly.
Passages like the one above are common in Nicholas Nickleby: the narrator begins by giving readers insight into a character's thought process ("[Kate] was undoubtedly handsome" and to pursue her would "enhance his reputation with the world"). The narrator then follows this insight with analysis, employing either a satirical or didactic tone to make a broader statement about society or human nature. In the above passage, the narrator uses this didactic tone to depict the causal relationship between Mulberry's social circle of "yes" men and his attitude towards Kate.