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.