Herodianus of Syria (170 - 240 AD) was a contemporary writer of the same time as Dio Cassius. As he was not a political or social force, little is known of him.
His writing was a complete Roman history during his own lifetime up to about 238 AD, but it lacked organization and chronologic uniformity. Dio Cassius is generally the preferred writer of the time, but Herodian should not be dismissed.
Some of his work, as stand alone pieces, provides valuable insight such as his treatment of Elagabalus. Additionally, as a Syrian, he focused heavily on some eastern campaigns, providing excellent source material for Parthia and surrounding territories.
History of the Empire