Perhaps OK to begin with him,but I would be cautious citing him as a prime source, as I would indeed with citing ANY single ancient source as conclusive evidence. In brief, Josephus seems to have been a ruthless opportunist and Roman apologist.
The discipline of history as we know it began roughly with Edward Gibbon. (1737-1794)
Before that time it was understood that accounts of people and events were unlikely to be objective or necessarily truthful.
"Josephus (AD 37 – c. 100), also known as Yosef Ben Matityahu (Joseph, son of Matthias) and, after he became a Roman citizen, as Titus Flavius Josephus, was a first-century Jewish historian and apologist of priestly and royal ancestry who survived and recorded the destruction of Jerusalem in AD 70. His works give an important insight into first-century Judaism.
Josephus was an important apologist in the Roman world for the Jewish people and culture, particularly at a time of conflict and tension. He always remained, in his own eyes, a loyal and law-observant Jew. He went out of his way both to commend Judaism to educated Gentiles, and to insist on its compatibility with cultured Graeco-Roman thought. He constantly contended for the antiquity of Jewish culture, presenting its people as civilised, devout and philosophical. Eusebius reports that a statue of Josephus was erected in Rome.
Josephus's two most important works are The Jewish War (c. 75) and Antiquities of the Jews (c. 94). The Jewish War recounts the Jewish revolt against Rome (66–70). Antiquities of the Jews recounts the history of the world from a Jewish perspective. These works provide valuable insight into first century Judaism and the background of early Christianity."
Josephus is often cited by apologist for proof of the existence of Jesus:
"Jesus of Nazareth is possibly mentioned in two passages of the work The Antiquities of the Jews by the Jewish historian Josephus, written in the late first century CE. One passage, known as the Testimonium Flavianum, discusses the career of Jesus. The authenticity of the Testimonium Flavianum has been disputed since the 17th century, and by the mid 18th century the consensus view was that it had at a minimum been altered by Christian scribes, and possibly was outright forgery. The other passage simply mentions a Jesus as the brother of a James, possibly James the Just, but later in the same passage refers to a Jesus, son of Damneus. Most scholars consider this passage genuine, but its authenticity has been disputed by Emil Schürer as well by several recent popular writers."