Cassius Dio or Dio Cassius (c. 155 – c. 235) was a Roman statesman and historian of Greek origin. He published 80 volumes of history on ancient Rome, beginning with the arrival of Aeneas in Italy.
No, it's not for reading for fun, but a great primary source for history papers, research, etc. Get an electronic version free at Project Gutenberg and use the search function to find quotes to support your thesis.