Devarim is Moses' instruction to the people about to enter the Promised Land, on the verge of Redemption. It is the Book of When We Are Preparing for Moshiach.
The five books of Torah are the blueprint for creation. Properly understood, each book presents one dimension of the vast eternal plan. In his published sichos (talks) on the weekly parsha, the Lubavitcher Rebbe reveals the theme of each book.