Some encouragement to dive into Isaiah for a while:
“If you have any interest in the Bible at all, Isaiah will reward close reading” (Ray Ortlund, Jr. Isaiah, 17).
“Isaiah is probably the most important prophetic book for the New Testament” (Rikk Watts, Lecture)
“There is no other book in either Testament which comprehends the whole of biblical theology so completely as does Isaiah” (John Oswalt, “Isaiah,” New Dictionary of Biblical Theology).
“Of all the books in the OT, Isaiah is perhaps the richest. Its literary grandeur is unequaled. Its scope is unparalleled. The breadth of its view of God is unmatched. In so many ways it is a book of superlatives” (John Oswalt, Isaiah, 3).
“The book of Isaiah in many ways is the centerpiece of the story of Israel in the biblical story (Stewart and Fee, How to Read the Bible Book by Book, 174).
“For sheer grandeur and majesty probably no book in the Hebrew Bible can be compared with Isaiah” (Longmann and Dillard, Introduction to the Old Testament, 267).
“…What is arguably the most theologically significant book in the Old Testament” (Barry Webb, The Message of Isaiah, 13)
“When asked by Augustine which book of the Bible should be read first, Ambrose responded, ‘Isaiah’” (Seitz, Isaiah 1-39, 1).
…but don’t take their word for it.