Not long ago I wrote a brief article on “The Historical Jesus” for the E3 Foundation. It is a basic introduction to the question what is known about Jesus outside the New Testament. I survey what Roman and Jewish sources are saying about Jesus in the decades and centuries after his execution. The Romans considered Christianity a dangerous superstition. The Jews considered Jesus a false Messiah. The Christian texts consider Jesus the Son of God. Ironically, all these texts are biased one way or another, but you do find some important correlation between them.
Here is a link to that article: