Isaiah 40–66, by Marvin A. Sweeney, is the nineteenth published volume in The Forms of Old Testament Literature (FOTL), a series that provides a form-critical analysis of the books and units in the Hebrew Bible. Building on his earlier FOTL volume Isaiah 1–39, Sweeney here presents his analysis of Isaiah 40–66 within both the synchronic literary form of Isaiah and the diachronic history of its composition. In keeping with the methodology and goals of the FOTL series, Isaiah 40–66 offers detailed examinations of the formal structure of the chapters covered; the genres that function within these chapters; the literary, historical, and social settings of the text; and the overall interpretation of Isaiah 40–66 and its constituent textual units. Including a glossary of the genres and formulas discussed, this commentary will be a useful resource to anyone wishing to engage more deeply with this central book in the Hebrew Bible.