With this week's reading we launch into the books of the prophets that will take us to the end of the Hebrew Bible/Old Testament. The word "prophecy" derives from Greek roots meaning "to speak for" - thus a prophet is one who speaks for God. The sense of "prophecy" as foretelling the future is a component of the prophet's work, but in the Bible it is the result of the prophet's primary work, not the primary work itself. In other words, a prophet speaks God's perspective on the present situation of God's people, and then points to the consequences of that perspective - the future that will result from what God thinks of this present. Thus the prediction aspect of prophecy is not meant to be the center of the performance of the prophet - rather, how well the prophet conveys God's words, God's meaning, God's purposes.
The Book of Isaiah is the first of the great prophets. But while there is general agreement that much of the book was written by the self-identified Isaiah son of Amoz, the writings themselves cover a span of something around three centuries. Three broad divisions are usually acknowledged. First Isaiah, chapters 5-39 (with many scholars arguing for a variety of exceptions, seeing some of these chapters as belonging to the later figures), was written between ca. 750 and 700 BCE, in the context of the divided kingdom (Judah in the south and Israel in the north) and up to the fall of Samaria (the capital of the northern kingdom) to the Assyrians. Second Isaiah, chapters 40-55, was written during the Babylonian Exile (586-538 BCE); and Third Isaiah, chapters 1-4 (though perhaps written by a later editor) and 56-66, was written after the return from exile (538 to mid-5th century BCE). Contemporary study Bibles provide even more divisions and historical contexts, but there is far from universal agreement on these.
Broadly, then, First Isaiah speaks of both God's promises to Israel and the threat of destruction caused by the people's turning away from God. Not to be missed, then, in this week's reading: the Song of the Vineyard in chapter 5 (a powerful metaphor for the people of Israel), Isaiah's original call narrative and vision of heaven in chapter 6, and the messianic prophecies of chapters 7, 9 and 11. The wonderful expressions of hope and faith in chapters 25 and 35 also relieve the otherwise rather doom-laden writings.