In this chapter, the sons of Jacob go to Egypt to buy grain, and Simeon is taken as a captive by Joseph.
Now that Joseph has achieved political power in Egypt and the famine has spread to Canaan, we are ready for the fulfillment of Joseph's dreams of supremacy in his family. This effectively concludes his story arc, forming a clear progression with 1) a defined-but-distant promise, 2) a series of challenges, 3) fulfillment of that promise.
We see how Jacob clearly values Benjamin over his other brothers. As I have previously said, this is because Benjamin is the only (known) son of Rachel who is still alive.
We see, yet again, how Egypt proves to be a refuge for Canaanites in times of famine. Abraham went down to Egypt during a famine and Isaac strongly considered going before God told him not to. Now Jacob is sending his sons to buy food from Egypt. The most probable reason for why Egypt is so consistently safe during famine is that Egyptian agriculture was heavily based around the Nile river and its delta, while farming in other regions was more dependent on unreliable rain patterns. While there were other rivers that could be used in agriculture, such as the Jordan or the more distant Tigris/Euphrates system, the Nile was generally the largest and most exploited of the ancient Near East rivers.
Probably the most confusing thing to new readers is why Joseph wishes to deceive his brothers. We can (implicitly) tell that Joseph's appearance must have changes a whole lot in the many years he was in Egypt. We know he was sent there as a youth, possibly only 8-12 years old, and now he is 30, is wearing rich clothes, and is fluent in Egyptian (which is another sign he must have been sent young, because he was able to learn the language relatively fast and completely). So it's pretty reasonable that they don't recognize him.
But why would Joseph lie to them and threaten them? I think the best answer is that he was somewhat lonely and the only brother he ever got along with is his own mother-brother, Benjamin (both sons of Rachel). Probably Benjamin had the least to do with betraying Joseph. My guess is that Joseph wanted to have them bring Benjamin down to Egypt, and then have all the other sons return to Jacob and then Joseph would live with Benjamin away from his family.
It's also interesting to see the arguments and the guilt they all feel about betraying Joseph when they sold him into slavery. They never before indicated they felt bad about it, but now the brothers lament how they ignored the "distress of his soul when [Joseph] pleaded with us". Reuben (who had tried to protect Joseph initially) chastises his brothers for not listening to him when he tried to stop them. Of course, it's easy to feel bad about something when you are suffering the consequences of your actions.
It is peculiar that Joseph returns the money into the grain sacks of all his brothers. I'm honestly not sure what he was intending. Maybe he wanted to bless them with free money. It is ironic that what is intended as a gift terrifies his brothers so much. His brothers are of course scared because they think that they were given the money by accident and that Joseph would think they stole it. Joseph has all the power, so he could have them killed if he wanted.
It's funny to see the nervous honesty of Joseph's brothers in the face of his power over them. It is different behavior from a group of brothers who were repeatedly defined by their lies and deception to now be desperately honest in spite of circumstances that make them appear as if they were thieves, and even furthermore being accused by Joseph of spying on the land. Not only are they suffering for their actions towards Joseph, they are possibly also suffering because of their lifetimes of deception. One can wonder if Joseph is doing this intentionally, since he knows their character.
I also love how Reuben stands up to his father on behalf of Benjamin. Before now, we have never seen the sons of Jacob take responsibility for anything or anyone. We have heard Joseph share a "bad report" about them, and we have personally observed the lies and bloodshed of Simeon and Levi and the various sins of Judah. We also saw the sons of Jacob "staring at one another" in verse 1, clearly showing their hesitancy at taking responsibility for getting food. Yet now Reuben is swearing by his two sons that he will protect Benjamin on behalf of his father when they go down to Egypt. This is in addition to his (halfhearted) attempts to protect Joseph some decades earlier. So Reuben is one of my more favorite sons of Jacob for that reason.
Nevertheless, it is too much of a risk for Jacob and he refuses Reuben's offer.