Why does the book of Devarim have the structure it does: a mix of history, law, recollection and anticipation?
The sages knew that Devarim had a clear structure. Elsewhere in the Torah some rabbis used the principle of semikhut haparshiyot -- that we can learn something from the fact that passage Y occurs immediately after passage X. Others however did not, because there is a rule, ein mukdam umu'achar baTorah, meaning, the Torah does not always follow a strict chronological sequence. So we cannot always attach significance to the fact that the passages are in the order they are. However, everyone agrees that there is precise order and structure in the book of Devarim (Berakhot 21b). But what is the order?
Second: the sages originally called Devarim Mishneh Torah, a "second law". Hence the Latin name Deuteronomy, which means, the second law. But in what sense is Devarim a second law? Some of the laws Moses states in the book have appeared before, others have not. Is it a repetition of the laws Moses received at Sinai and the Tent of Meeting? Is it something new? What exactly is the meaning of Mishneh Torah?
Third: what is the book doing here? It represents the speeches Moses delivered in the last month of his life to the generation who would cross the Jordan and enter the Promised Land. Why is it included in the Torah at all? If the Torah is a history book, then we should proceed directly from the end of Bamidbar, the arrival of the Israelites at the banks of the river Jordan, to the book of Joshua, when they crossed the river and began their conquest of the land. If the Torah is a book of law, then Devarim should just be a collection of laws without all the historical reminiscence and prophecy it contains.
What kind of book is Devarim and what is its significance to the Torah as a whole.