Welcome to Deuteronomy, the fifth and final book of the Pentateuch. :)
Deuteronomy is Greek for "second law", and that's precisely what it is: Moses giving us a second recounting of the Law.
Deuteronomy follows in the footsteps of the earlier books of the Pentateuch and it has the same variegated style: there's some history, exhortation, laws, poetry, prophecies, a song and dance routine, etc (well, everything but that last part). It's a real production.
More significantly, Deuteronomy follows the Hittite structure of a suzerain/vassal treaty, reaffirming the covenant between Israel and the LORD*. This is really what ties it all together as all of the songs and poems and laws and warnings are really about encouraging the Israelites to follow the LORD and defining their relationship to him. The history establishes their past, what the LORD has done for the nation. Their fathers' rebellion and punishment in the desert is a warning to obey the LORD. All of this can best be understood as a restatement of the covenant for a new generation. I will reference the various portions of the suzerainty treaty format as we progress through the chapters of Deuteronomy.
I think it's important to put Deuteronomy in context of the larger biblical history. Genesis is the book of introductions, giving us the history of the world with Adam, Eve and so on, then the beginning of the covenant with Abraham and God, leading up to the Israelite migration to Egypt. Exodus gives us the exodus from Egypt, as the Israelites are suddenly and miraculously freed from slavery and led on a journey towards the promised land. Exodus ends with a long, elaborate description of the tabernacle and its construction. Leviticus is a legal interlude, teaching us how to offer sacrifices and many rituals related to the priestly duty, plus some other stuff that isn't related. Numbers continues with the story from Exodus, as the first generation sins against the LORD by refusing to take the promised land. They are condemned to die in the wilderness and that a new generation would arise to take the promised land. Moses is also condemned to never enter the promised land because of his own sin. Forty years pass and the nation marches upon the promised land once more, defeat two Amorite kings and now encamp on the plains of Moab east of the Jordan, ready to claim their inheritance.
Deuteronomy as a book is entirely composed of Moses giving warnings, exhortation and commands to the people because the LORD forbids him to enter the land. Therefore this book takes place outside of the promised land and contains little, if any, of a direct story. We can also understand why Moses is recounting the law and history of Israel, because this new generation is possibly not familiar with it. This also explains the polemical style, because Moses is speaking directly to the people who are about to cross over.
Stylistically, Deuteronomy is very different from the earlier books of the Pentateuch. The polemical style is one aspect, which emphasizes a mixture of first and second person as Moses recounts what "I said to you". This is strange to a lot of readers at first, because I just said that this is for a new generation who weren't present when these earlier events occurred. The reason Moses is using a second-person narrative is to heighten the immediacy and responsibility for what happened to the current generation. That is, if Moses were recounting it in third person, "I said to your fathers..." then the current generation is given a chance to disavow their past and claim innocence. The style here is intended to be a bit more accusational, saying "You have sinned in this way, but the LORD has shown you mercy; therefore obey the LORD and his commandments".
It makes a stronger demand on the listener to be positioned within the story, and it also connects the listener more strongly with the past. To use a second-person narrative places the listener within those past events to show how strongly their current position is tied to their past.
In addition, we should understand that this is another aspect of the communal nature of Israelite society. It is a single nation both in the prior history and the "present" history to Moses's audience. Moses isn't addressing a specific person, he is addressing a people, and while the composition of that people changes over time, it is still the same nation throughout its history.
This polemical style is presented most ironically in Deut 5:2-3 when Moses says, "The LORD our God made a covenant with us at Horeb. The LORD did not make this covenant with our fathers, but with us, all those of us ourselves." This is not literally true if we think that the covenant was made with their fathers, who died in the wilderness. I don't think that's the right way to view it, because what Moses is trying to do is establish the covenant as a multi-generational treaty. If you think of the covenant as something established with your fathers, then when your fathers die, the covenant dies with them. That's why to Moses and his listeners, the covenant is established with you, because that's the only way the covenant can endure from generation to generation, as it was originally intended (among other references, see Ex 12:24 to 12:27 which establishes the permanence of the Passover from generation to generation).
Another difference between Deuteronomy and the other books is that Deuteronomy is largely forward-looking, preparing the Israelites for their possession of the promised land. If Numbers is a book that employs militaristic language and stories to show their preparedness for the coming battles, Deuteronomy is a book that prepares the Israelites for their occupation and settlement of the promised land. For example, there is a recurring phrase in Deuteronomy, "the place which the LORD God will choose for his name to dwell" (Deut 12:11) and minor variations on the same theme. This phrase occurs around 20 times in Deuteronomy and it signifies the future location of the temple.
This is really significant so I will take a moment to explain. The tabernacle is literally a tent, a portable structure that is broken down and reassembled as needs be, while the Israelites march for years through the Arabian desert. When the Israelites permanently settle in the promised land, it is unlikely that the tabernacle will need to move anymore and a permanent structure becomes both possible and desirable. It is possible they could just set the tabernacle down somewhere, or they could build a new structure altogether. Either way, the location of the temple will have significant political and religious ramifications as it would establish a major power center in Israel.
It should be evident to my readers that this is yet another element of the "settlement and occupation" theme in Deuteronomy. There would have been no concern for a permanent residence of the tabernacle when wandering in the desert, because the whole nation had no permanent residence. So it is actually quite rational that Moses would start planning for this eventuality now, on the eve of their invasion and the end of his life.
Generally speaking, liberal scholars typically consider this phrase is a veiled reference to the temple in Jerusalem. I.e. that Deuteronomy, written after the construction of the temple, has these thinly veiled references inserted to help validate the existence of the temple itself. Therefore the religious figures of that time could take Deuteronomy (a book secretly of their own invention) as proof that the temple (their center of authority) was validated by God. A power play, essentially.
I think I have shown above why this theory is extraneous. The entire nation of Israel is transitioning from a nomadic pastoral existence to a much more static farming society with small bits of urbanization including numerous Levitical cities taken from the other cities of the Israelites (Num 35:8: "each shall give some of his cities to the Levites..."). There are many other provisions related to this new static existence, such as the various laws on inheritances and the division of the land we saw in Num 34-36, and many more in Deuteronomy itself. It is only natural that, with everything else shifting towards a more permanent basis, the tabernacle itself would transform into something more enduring. In my opinion, it is unnecessary to draw upon priestly collusion to explain this shift in tone.
Overall, there is a lot of similarity between Deuteronomy and sections of Exodus, Leviticus and Numbers. I will try to point out the parts that are similar, differences between these sections, and whenever we encounter an entirely new section in Deuteronomy. And with that, I will begin the last book of the Pentateuch.
* JEDP theorists will disagree with this point, but it is far beyond my scope to properly analyze the relative merits of these two theories. There are many good sources on this topic and I would encourage any interested readers in looking elsewhere. For instance, here. Essentially, the JEDP theorists emphasize the patchwork composition as evidence that it comes from multiple authors or layers of composition. Traditional scholars emphasize the treaty/covenantal form and explain the patchwork appearance as modern sensibilities being misapplied to a genuine text.