First, it is important to emphasize that there really is nothing original in Rabbi Boteach's book. There is a curious phenomenon when it comes to Jesus of a collective amnesia on the part of those selling material on Jesus to the general public as to what has been written before. Scholars are constantly being reported as unraveling new understandings of Jesus when there has really has been nothing new in the field of Jesus since the important discoveries of the Dead Sea and Nag Hammadi scrolls more than fifty years ago. Even in these cases, such discoveries simply offered hard evidence for what scholars had long suspected that the early Christians had much in common with other Jewish sectarian groups from the period and that they were a diverse group of people with proto-orthodoxy being one of many competing sects. Academic scholars for over a century now, since at least from the time of Albert Schweitzer, have focused on Jesus as a first century Jew. Scholars such as Morton Smith and Geza Vermes have pioneered the use of Jewish texts such as the Talmud and Midrash as keys for understanding Jesus.
For that matter, Christian scholars, particularly Protestants, have long since been actively conscious of Jesus' Jewish identity. Martin Luther famously wrote an early philo-Semetic work That Jesus Christ was Born a Jew. (This was before his later infamous work The Jews and Their Lies.) For the most part, Protestant interest in Jesus' Jewish identity has led to philo-Semitic attitudes toward Jews down to today. A critical part of Protestant philo-Semitism, including Evangelical support for the State of Israel, is that Protestants strongly identify with the Old Testament and by extension with the people of Israel as the nation that produced Jesus. Furthermore, from almost the beginning of the Reformation, Protestant theology broke down the rigid distinction between the triumphant Church as the true Israel and the synagogue as a religious relic. This was largely due to the fact that Protestants rejected the notion of a visible Church of the saved. If it was no longer clear that Christians were saved then Jews stopped being particularly remarkable or satanic for being damned or at least not yet visibly saved.
Early Modern Protestant philo-Semitism should give one pause from drawing a straight line between the charge of deicide and anti-Semitism. One could embrace Jews precisely for their role as depraved sinners against God, representing the depraved hearts of all humanity as it rebels against God. If Jews could antagonize God throughout the entire Old and New Testaments and still be his beloved people for whom he has left open the possibility of salvation, then they should be embraced by Christians (who are also utterly depraved sinners) as a symbol of hope for their own salvation. From this perspective, the whole question of Jewish responsibility is beside the point. It matters little what blows first century Jews physically struck against Jesus or how they called for his death. Jews (along with everyone else) caused his death by rejecting him and making his sacrifice necessary. Theologically literate Christians, the kind that Jews might wish to talk to, already understand this. Jews need to get over this issue and stop being paranoid that they are being blamed for killing someone's Lord and are about to be sent to gas chambers for it. Unfortunately Rabbi Boteach exemplifies precisely this sort of problematic attitude. Much of the book is devoted to proving that the Jews were not responsible for the death of Jesus, that the Romans were the true villains of the story and that the Church distorted this fact.
The problem with writing about Jesus is that it is essentially impossible to say anything new because everything that might possibly be said has been said. Whatever Jesus you want, communist revolutionary, conservative capitalist or liberation feminist, you can find scholars who can give you your own Jesus tailor made. This illustrates a fundamental problem with trying to discover the "historical Jesus;" the canonized Gospels represent a web of contradictory information and this problem only gets worse once the non-canonized Gospels are brought into play. Anyone making definitive claims about who Jesus was and what he preached beyond the fact that he was a Jewish preacher from the Galilee can be dismissed from the beginning as missing the point.
It is thus laughable for Rabbi Boteach to strive onto the field with barely a nod to biblical scholarship and claiming to offer a definitive answer as to the real Jesus. The one author that Rabbi Boteach demonstrates a close reading of is Hyam Maccoby, whose polemical work was hardly representative of the field. A good example of how Rabbi Boteach tries to force through the conclusion that Jesus was a good Pharisee is his claim that the reason why Jesus allowed his followers to pick grain on the Sabbath was because they were in danger of starving to death because they were patriotic rebels on the run from the Romans. Rabbi Boteach also claims that Jesus making inferences from simple to more difficult cases is evidence of his using Pharisaic logic. This may be the true story, but there is no evidence for it and it turns the Gospels intent on its head.