Another apropos to our upcoming discussions about How Rome Fell: Death of a Superpower by Adrian Goldsworthy:
Herodian (c.170-c.240): Greek historian, author of a History of the Roman Empire.
Jona Lendering of livius.org has information:
Herodian's life is almost unknown to us, but we can reconstruct several elements of it from his History of the Roman Empire since Marcus Aurelius, which is a lively and accessible book that might also have been titled Crises in Rome, as it describes the Year of Five Emperors (193) and the Year of Six Emperors (238).
The text of the History can also be found on that site: Herodian's Roman History.
Image: Alexander Severus. Marble, Roman artwork, 222–235 CE.
Capitoline Museums, Rome