Those readers acquainted with biblical scholarship know that there is a general consensus that the book of Isaiah was not entirely penned by the eighth century BCE prophet. That the book underwent some kind of editing is virtually undisputed. For example, chs. 36-39 contain material lifted directly from the Deuteronomistic History (i.e. 2 Kings 18-20), suggesting that someone inserted this material into the oracles of Isaiah. But it is also more than that; much of the book of Isaiah seems to belong to an era after the life of the prophet. For example, in ch. 40 there is a shift in tone from judgment in the previous chapters to comfort and hope in 40:1. The language used is suggestive of an exilic or even post-exilic period, not pre-exilic. This along with multiple other lines of evidence have caused scholars to divide the book of Isaiah into three parts: Proto or First Isaiah (chs. 1-39), Deutero or Second Isaiah (chs. 40-55), and Trito or Third Isaiah (chs. 56-66).
First Isaiah, though containing some material not penned by the prophet (e.g. chs. 36-39), was almost certainly written by a historical person who lived during the reign of multiple kings (cf. Isaiah 1:1). The material in First Isaiah, then, are of great historical importance since they reflect the life and times of someone intimately familiar with the Judean court (cf. 2 Kings 19). These texts are nearly three thousand years old and worthy of study. And the team at Yale Bible Study has put together a video series doing just that. It features two prominent biblical scholars, John Collins and Joel Baden, and their discussion of First Isaiah, rooting it in its own historical context. The first video in the series is posted below but the series itself is eight videos long with each video being around fifteen minutes. If you’re interested in historical criticism and the Hebrew Bible, this series is a great way to become familiar with its application in the context of the book of Isaiah.
 For an overview of Isaiah, including why scholars think much of it was not written by the prophet Isaiah, see Michael D. Coogan, The Old Testament: A Historical and Literary Introduction to the Hebrew Scriptures, third edition (Oxford: Oxford University Press, 2014), 331-333.