A little thought about the change from the first 4 books of the chamisha chumshei Torah to the last sefer... Devarim.
Before it was Israel mucking up and Hashem chastising and punishing Israel with Moshe as Israel's defender.
Now it is Moshe that is chastising Israel and not necessarily with the help of God, and albeit without the power to punish.
Sefer Devarim is written from Moshe's historical perspective and context. So now we see somewhat the human side of the problems that plagued Israel in the prior 40 years. Sometimes it is not always the best way to be judged by a non-peer because that person does not understand human frailties.
Moshe had the right to speak on his own behalf, it was his books that were written, and talk to the people on the level of the people. The task is not easy but must be done. Humans need to be challenged by humans in order to be better. We can aspire to be God-like but we can never attain that level.
Moshe's final book of Deuteronomy is our human way of dealing with God and Torah and making ourselves better for it.
