The central theme of the book is God himself, who does all things for his own sake (48:11). Isaiah defines everything else by its relation to God, whether it is rightly adjusted to him as the gloriously central figure in all of reality (45:22–25). God is the Holy One of Israel (1:4), the One who is high and lifted up but who also dwells down among the “contrite and lowly” (57:15), the Sovereign over the whole world (13:1–27:13) whose wrath is fierce (9:12, 17, 21; 10:4) but whose cleansing touch atones for sin (6:7), whose salvation flows in endless supply (12:3), whose gospel is “good news of happiness” (52:7), who is moving history toward the blessing of his people (43:3–7) and the exclusive worship due him (2:2–4). He is the only Savior (43:10–13), and the whole world will know it (49:26). To rest in the promises of this God is his people’s only strength (30:15); to delight themselves in his word is their refreshing feast (55:1–2); to serve his cause is their worthy devotion (ch. 62); but to rebel against him is endless death (66:24).
ESV Study Bible, p.1234