The Book of Daniel, although included in all Christian Biblical Canons, was not included in the original Hebrew Canon. Theologians and Biblical historians have debated many reasons for this, most of which don't have to do with the Book's message as much the time and location of its writing. The Book of Daniel has strong thematic similarities to the rest of the Old Testament, and even a relevance to the New. It repeats themes from Job, Ruth, Genesis and Exodus, sometimes very blatantly and sometimes more subtly.
One of the most obvious parallels one can draw is between Daniel and the story of Joseph in Genesis. Both Daniel and Joseph travel to a far-off land (Egypt for Joseph, Babylon for Daniel), where they are subdued in some way or another (Joseph in prison and Daniel as a servant). They both gained favor with the local monarch (Pharaoh for Joseph and King Nebuchadnezzar for Daniel) by interpreting important visions.
Both practice the will of God through politics. Both remain devoted to the Judaic God during their reigns, and both are mentioned alongside royal pagan priests to show the divinity of the Judaic God and the falsehood of all the others. Since many of the formative years of the Hebrews were spent under foreign subjugation, both stories highlight how a Jew could succeed even if deprived of his homeland.
Although the structure and tone of Daniel and Job don't bare any similarity to one another, their message does. Daniel and his compatriots undergo various tests of faith. When Nebuchadnezzar orders the people of Babylon to worship a giant golden idol, the Chaldean nobles pointed out that three Jews had not worshipped his statue: Shadrach, Meshach and Abednego. As a result, they are cast into a great furnace, but are unscathed. When...