There are large numbers of objective, dispassionate and non-religious books about Jesus of Nazareth. The problem is that so little is known about Jesus, even from the Bible, that nearly everything is guesswork.
Some, like
Did Jesus Live 100 B.C.? (G. R. S. Mead), look for evidence of an underlying legend in the Dead Sea Scrolls.
Did Jesus exist? (G. A. Wells) and
The Jesus Puzzle: Did Christianity Begin with a Mythical Christ? Challenging the Existence of an Historical Jesus (Earl Doherty) are among many that investigate evidence that Jesus of Nazareth never really existed.
The Homeric Epics and the Gospel of Mark (Denis R. MacDonald) is a highly readable and well-researched book that examines parallels between the original gospel, Mark's Gospel, and the Homeric Epics, the
Iliad and
The Odyssey. This is one of many that consider that Jesus of Nazareth was a literary creation of the author of Mark's Gospel. Here, the view is that Paul, in his epistles, had been talking about a purely spiritual Jesus, just as we find in
Hebrews.