In Chapter 17 to 24 in book 2, what is Dickens point of view, and how is it changed?
As an omniscient narrator, Dickens is free to focus in on a particular time and follow characters around, being privy to their emotions or feelings, and then shift focus as and when he wants. Such a shift occurs at the beginning of Chapter 21, where, having focussed in on Lucie and Charles Darnay and their family, Dickens fast-forwards the action quickly, narrating how the Darnays spend their first few years of marriage together, and have children. Lucie is described in these years as being engaged in her own task, which gives the second book his title:
Every busily winding the golden threat which bound her husband, and her father and herself, and her old directress and companion, in a life of quiet bliss, Lucie sat in the still house in the tranquilly resounding corner, listening to the echoing footsteps of years.
Thus the time advances through these "echoing footsteps of years", and sets the scene for a shift in focus, which comes half-way through this chapter, after Darnay and Mr. Lorry have commented on disturbing rumours of what is going on in Paris. The tranquility of this household family scene is sharply constrast with the sudden switch to France and the beginning of the Revolution in the Defarge wine-house, the storming of the Bastille and the beginning of the rise of the "sea" that is metaphorically referred to in this chapter to describe the unstoppable and unyielding nature of the patriots as they gain their revenge.