Isaiah 1:1 reads, “The vision of Isaiah son of Amoz, which he saw concerning Judah and Jerusalem in the days of Uzziah, Jotham, Ahaz, and Hezekiah, kings of Judah” (NRSV).
Scholars remain divided as to whether or not this “vision of Isaiah” verse is meant to apply to all 66 chapters, or whether Isaiah might be the author of just the first 39 chapters, with other authors (in the tradition of Isaiah) having penned chapters 40-55 and 56-66.
I’ve long had my eye on The Eerdmans Companion to the Bible and have begun using it recently. Its introductory section to Isaiah had what I thought was a refreshingly balanced approach to the issue of authorship in Isaiah:
Taken as an introduction to the book as a whole, Isa. 1:1 identifies the contents of the subsequent 66 chapters as the “vision” of 8th–century Isaiah. But modern scholars have challenged the traditional view that considers him the source of all the material contained in the book that bears his name. Though chapters 40–66 echo certain themes contained in chapters 1–39, they also contain specific, predictive prophecies that some scholars doubt Isaiah foretold. For example, they consider it unlikely that an 8th–century prophet not only predicted the 6th–century Persian king Cyrus’s conquest of the Babylonian Empire but also named him specifically (see 44:28 and 45:1). Old Testament prophets normally directed their messages to contemporaries. For Isaiah to have directly addressed the Babylonian exiles (and perhaps returnees to Judah) pictured in chapters 40–66, his prophetic ministry would have to have extended well beyond the reign of Hezekiah (the last king mentioned in 1:1), and he would have to have lived for more than two centuries.
On the other hand, in this book God holds out his power to predict the future as proof of his divine supremacy (chs. 41, 44, 46, and 48). It is not unreasonable, therefore, to think that Isaiah mediated predictive messages as words from God and at times addressed audiences of future generations.
More details on this Bible guide are here at the Eerdmans page. I’m finding that it’s a concise yet substantive way to get myself oriented to a given book of the Bible.