The final eighteen books of the Old Testament are the books of the prophets, which is not to say that these are the only prophets we know of. A number of prophets are mentioned in the other books – Elijah and Elisha in the books of Kings, Baalam (Numbers 22-24), Aaron in the book of Exodus. There is an extensive list in Wikipedia. The books of the prophets are all named for men but a number of women are named in the bible as prophets (see here).
The prophetic books contain the prophecies, and sometimes stories from the lives, of a number of significant prophets but the nature of the writing is far from consistent throughout. Some of the prophets speak their prophecies, others act them out. Some of their writings are in prose, but much of it poetry; some use metaphor or parable, others speak clearly and directly. Some of the books contain the sayings of the prophets, others contain the writings and reminiscences of their followers or disciples. Some of the works (Daniel and parts of Ezekiel) are more like apocalyptic literature (see the Book of Revelation in the New Testament) than prophecy.
These eighteen books come from an enormous range of Israel’s history, starting with the early days of the two kingdoms (931 BC) through the days of the exile (late 8th C.), restoration (538) and with the last book written during the days of the Hellenistic period from 323-63 BC.
The messages of the prophets are as varied as the times in which they lived – and that is the key to understanding what they said. Each of the prophets was addressing his message to the situation in which he found himself. The issues he cared about and spoke about were the issues facing his contemporaries.
Most of the books are quite short but three stand out simply because of their length – Isaiah, Jeremiah and Ezekiel.
Isaiah has always found popularity among Christians and passages from his prophecies are often read at Christmas and during Holy Week. Although those readings (e.g. Is. 7.10-16; 9.2-7; 52.13-53.12 and many others) clearly reflect Christian teaching and belief about the person of Christ and the events surrounding his birth and death, it is unlikely that Isaiah considered himself to have been speaking about things that would happen seven centuries later – he was addressing himself to his contemporaries and the issues of his day.
Jeremiah’s prophecy is typical of much that we find in many of the prophets as he reminds his contemporaries of the likely outcome of their disobedience to their God, and he addresses his words first to those who will be deported, as a warning, and then to those in exile, as words of hope of restoration.
These prophets, like all of the others, are looking at their world and addressing themselves to their contemporaries. That so much of their messages remain relevant and challenging to us today is surely because, in spite of all the progress that has been made, human beings are still, well, human. The political issues of our day – justice, immigration, wealth, poverty integrity, war, right management of the environment – are not so very different from the issues spoken about in the days of the prophets. The religious issues remain the same – faithfulness, purity, morality, religious practice, relationship with the world. The prophets speak most clearly to the human condition, and that message can always be found and applied as readily to our context as it applied to their own.