A whole lot of non-academic books dealing with the "historical Jesus" have been published over the past 15 years. Each seems to be grinding an axe of some sort, despite their purported attempts to present an unbiased historian's interpretation of the life and times of Jesus of Nazareth. Some are obviously supporting the traditional Christian interpretation of Jesus as the Christ, the Lord and Savior. Some others paint Jesus as a social and political reformer, someone who was out to promote a secular vision similar to our modern "-isms" (e.g., socialism, universalism, feminism, pacifism, communism, or maybe even capitalism!), despite all the God talk.
Professor Ehrman, by contrast, tries to popularize what appears to be the modern academic consensus: that Jesus was one of many Jewish apocalyptic prophets who preached and gained a following in Roman Palestine. Like the others, Jesus was convinced that God was angry about the continuing sins of the Jews and about the Romans trampling upon the Holy Lands, and was about to come down from the sky and establish a righteous kingdom of His own. Not a kingdom in the heavens, but one right there in the hills of Galilee and on the streets of Jerusalem. There was going to be a mighty judgement when this happened: good people could stay and flourish, but the bad were gonna get cast into a pit of fire or something. It was all about ancient Judiasm, all about the fulfillment of scriptural prophecies. It had little to do with later Christian beliefs or Enlightenment-age theories about how the world should be run.
I personally found this book to be monumental. It's one of that handful of books that you read in your life that opens your eyes and puts a lot of puzzle pieces into place. HOWEVER . . . . . this is not to say that Professor Ehrman has written the definitive biography of Jesus. I still think that he misses some important things and suffers himself from certain biases that distort the picture somewhat. The biggest problem is that Professor Ehrman ultimately assumes that Jesus was much like his friends in academia: a sober, reasonable fellow with whom you could have a polite, well-informed conversation about worldly matters. Ehrman forgets that if Jesus was an apocalyptic, he was probably much like the modern apocalyptics that are described at the start of the book -- i.e., people with fire in the belly, people quite sure of their beliefs even when based on conjecture and fantasy. I.e., someone you might call a fanatic, even a "nutcase". In Jesus' case, at least, someone passionate about the holy, irrationally in love with God.
So it's a bit strange when Ehrman strongly asserts that Jesus didn't think of himself as the Son of Man (or perhaps more accurately, the Son-of-Man-in-training). According to Ehrman, that notion had to have been made up by the Christians later on, after Jesus was long gone.
Ehrman argues that in the Gospels, especially Mark, language about Jesus' preachings seem to refer to the Son of Man in third person; i.e., Jesus was talking about someone else. However, in other places, Jesus clearly refers to himself as the Son. Ehrman reasons that Christians wouldn't have made up Jesus' third-person referral to the Son (since it would militate against their view of Jesus as God), but they certainly would have incentive to write about Jesus calling himself the Son. Ergo, any surviving third-party reference must be historical, and the other first-party references in Mark and the later Gospels must be made up.
Now wait a minute. If the early Christians were tweeking the text and inserting revised memories (and I agree that they probably were, up to a point), why were they so shy about the lines where Jesus seems to envision the Son of Man as someone else (e.g., Mark 13:26-27 and maybe 8:38 -- although that line implies some connection between Jesus and the Son)? Ehrman replies, "because it was the truth". But that fact arguably didn't stop the ancient Christian re-writers elsewhere.
I've got another theory. Some lines in the Gospels infer that Jesus taught his disciples things that he didn't share with the crowds (e.g., Matthew 13:17). What if Jesus believed that he was the Son (or was coming to believe it over time), but was a bit shy about announcing it to the masses (perhaps for fear of what eventually did happen to him, i.e. arrest and death)? What if Jesus shared this belief with his disciples, but was slow in proclaiming it to the crowds (until perhaps that fateful week in Jerusalem)? Then his followers would remember him as the Son, but the memory of his preachings might be a bit more circumspect. And that is just what we see, at least in Mark (which arguably has the most credibility as the earliest writing).
Another little irritation: Ehrman's homey, jokey, ultimately condescending writing style. He obviously wouldn't attempt such humor in a paper published in an academic journal. But when he appeals to the masses, he bends over backward to prove that he's a regular guy. It's OK at first, but it gets old real quick. Professor Ehrman: it might be better if you didn't try so hard to prove that although you're an academic superstar, you still know how to talk to dummies like me. The story about his son's rebuke for calling him a dude because "dude" also refers to a camel's gonads is something that should stay in the family. I can readily accept the proposition that words sometimes have two meanings without a sidenote about everyday teenage sarcasm.
Nonetheless, this book goes a long way in explaining who Jesus really was and what he was all about. It seems rather simple and obvious once you understand it, but it will be hard for many Christians to accept it. So perhaps that's why Ehrman tries so hard to be lovable to the average lout; a lot of average louts aren't going to love him once they get the gist of what he is saying in this understated but extremely powerful book.