Parshat Devarim is the beginning of the last book in the Torah. It starts with “Eilah HaDevarim,” “these are the words.” What exactly are these words? Rashi posits that “the words” are Moshe’s strong words of rebuke. Moshe begins his teachings here by subtly reminding his Bnei Yisrael of their many failures since the beginning of the Torah. Ramban offers an alternate answer, suggesting that “the words” are the commandments from Perakim 5-26 that form the bulk of Sefer Devarim. The first 4 Perakim serve as a preamble to “the words.”
Rabbi Zalman Sorotzkin presents a third answer. He notes that the second, third, and fourth books of the Torah are connected to Bereishit and to each other with the letter Vav. Sefer Devarim, on the other hand, does not begin with a Vav. The Torah is hinting to us that this last book is separate from the other four. Furthermore, the content of the last book is incomparable to that of the others. Much of Sefer Devarim is a recounting of the previous four books, which is why Chazal call Sefer Devarim the “review of the Torah.” The only connection that this book has to the other four is that all five books were written by Moshe in accordance with what Hashem told him.