So what of Isaiah as a whole? What is the main theme of the book? To me, I see primarily a book about God’s desire of righteousness and worship as opposed to meaningless ritual or especially outright rebellion. Isaiah (and possibly Deutero-Isaiah) wrote at and about times of great turmoil for the nation of Israel: The Syro-Ephraimite crisis and the end of the Babylonian exile. The prophet was concerned particularly that the people trust God for redemption rather than their idols / false gods, their neighbors, their things (weapons / wealth), or themselves (intelligence / might). The people of that time tended towards those things just as we do today. Isaiah wrote to guide us back onto the path towards God: Love God, do right, and maintain good habits (rituals), but be sure to use the ritual to keep your heart towards God rather than relying on them as an excuse to avoid God’s good orderly direction in your life.
And tomorrow: Jeremiah!