Halfway through this book it is in Aramaic, and therefore could no more be written by a contemporary of Nebuchadnezzar than a book that changes from Latin to Italian be written by Cæsar. In fact, it was written at least four centuries after the Jews were in exile and as such it is history masquerading as prophecy, and poor history at that.
i.1: Already the first verse is historically inaccurate as it was his son who was king. The third year of Jehoiakim's reign was 606 BCE, and it wasn't until 597 BCE that Nebuchadnezzar first invaded Jerusalem (although without destroying it). By then Jehohiakim was dead and his son Jehoiachin was in power.
i.7: Daniel was a eunuch, and despite the fact that Deut.xxiii.1 doesn't allow eunuchs to enter into the congregation of the Lord, he was a prophet.
i.9: The KJV states that God had brought Daniel into favour and tender love with the prince of the eunuchs.
The Hebrew words describing the two's relationship are chesed v'rachamim. The first word means 'mercy'. The latter could mean either 'mercy' or 'physical love'. As the writers would hardly write that Ashpenaz showed Daniel mercy, it should read instead that he 'showed mercy and engaged in physical love' with Daniel. Both were eunuchs, but as is mentioned elsewhere in the Bible, they still retain their sexual drive. There is no mention of another sexual partner either.
ii.4-7.28: These verses are in Aramaic which as mentioned above mean that another writer writing at a much later time and place composed it.
ii.35: The only way that the stone could become a great mountain that filled the whole earth was if the earth was flat.
iii.1: Nebuchadnezzar said to have built a statue of gold sixty cubits high and six cubits wide...