The Book of Daniel, as it is found in Protestant Bibles, is in 12 chapters which fall readily into two parts:

Most scholars maintain that the two parts of the book as we have it fit together to form a literary unity, designed to bring comfort to an oppressed people. The traditional view is that this unified book was written by a real prophet named Daniel during the Babylonian exile (c 570-536 BCE); but the more contemporary view is that it was written during the reign of Antiochus. For the former to be true, one has to accept that Daniel the Prophet literally foretold the future, including the rise of Alexander the Great. The latter view means that the authorship of a 6th Century BCE cannot be maintained. There are numerous references in the book as a whole to hardships and oppressions which were part of the Antiochan regime, including faith tests, issues over eating pork and the use of fire to punish. In tone, much of this writing is in accord with the Maccabean period. No significant scholarship proposes that the two parts were written separately, the first during the exile, the second during the reign of Antiochus.

Daniel is not linked by either Jewish or Christian Scholars with the writings attributed to him in the way that the great prophets are linked; and in the Hebrew Bible the Book of Daniel is placed in the third section on "Writings" not with the major prophets. Because of its vivid subject matter and its relevance to an occupied nation, it was perhaps the most popular book of the Bible after Isaiah during the lifetime of Jesus. As Christians we readily see its closeness to, or perhaps it influence on, the Book of Revelation to which its second part in particular bears close comparison.

Protestants have maintained that the book, as we have it, is the only genuinely inspired writing that can be included in a Book of Daniel because it is the only portion included in the Septuagint, although the version that we have of Daniel in the Septuagint was edited by Origen (died c254) for his Hexaphla (his version of the Bible in six versions). Most scholars now believe that three other texts can be included in the Book of Daniel, all from the Apocrypha, although most believe that the second and third were not by the same author as Daniel 1-12 and the first: