The prophetic books are a collection of books in the bible which contain speeches, or oracles, that were given by specific men to different groups of people living in different time periods. These men received these messages from God and delivered them to the people, often at a severe cost to themselves.
But these prophetic books can sometimes be hard to read because we don't always have a full picture of the events going on nor do we always grasp the dense poetry that the prophets often spoke with.
To get an overview of these prophetic books check out this video from
The Bible Project or you can view a playlist of videos which give an overview of several of the prophetic books.