"The Pickwick Papers"

Dickens' first major work is, to be honest, one of my least favorite. Reading Chesterton's eulogy, in chapter four of 'Charles Dickens, the last of the great men', it turns out that Chesterton admires this sort-of-novel for precisely the reasons that I did not like it: its lack of beginning and end.
Chesterton admires Dickens' characters, not the plots of the individual novels. As he states this on page 60:

Dickens's work is not to be reckoned in novels at all. Dickens's work is to be reckoned always by characters, sometimes by groups, oftener by episodes, but never by novels. You cannot discuss whether "Nicholas Nickleby" is a good novel, or whether "Our mutual friend" is a bad novel. Strictly, there is no such novel as "Nicholas Nickleby." There is no such novel as "Our mutual friend." They are simply lengths cut from the flowing and mixed substance called Dickens - a substance of which any given length will be certain to contain a given proportion of brilliant and bad stuff. You can say, according to your opinions, "the Crummles part is perfect," or "the Boffins are a mistake," just as a man watching a river go by him could count here a floating tower, and there a streak of scum.

Chesterton emphasizes that the 'primary elements' of Dickens are not the stories, but 'the characters who do not affect the stories': those characters who could enter in any novel at any moment, without essentially affecting the storyline (e.g. Major Bagstock). 
The enormous familiarity with which Chesterton speaks of all these characters is impressing; moreover, I feel motivated to reread several books by Dickens, in the hope of finding similar delights as Chesterton obviously did.