The book of Isaiah is actually three “books,” each written during a different time in Israel’s history.
Isaiah I: shape up or else; exile is coming chapters 1-39
Isaiah II: Book of Consolation, comfort in captivity chapters 40-55; also called Deutero (Second) Isaiah and contains the “suffering servant songs”
Isaiah III: going home chapters 56-66; also called Trito (Third) Isaiah; struggle for a new temple and new leadership
Date
The material in this book was most likely collected from the oral form and written down after the return of the exiles from Babylon.
Items of Note
I did the math one time. In a 3 year cycle of Sundays, the Old Testament reading is from Isaiah 25% of the time. We hear from Isaiah a lot!