Any attempt to characterize this book is like trying to bottle a whirlwind--it is a massive, heavily documented, and well argued case for a historical understanding of the origin of Christianity. Basically, Wright argues for: 1) a proper historical methodology, 2) a 2nd-temple Jewish background for Jesus & the N.T., and 3) a Jewish Messianic understanding of earliest Christian community.
According to Wright, there is no such thing as a totally "objective" neutral view of reality; and while the N.T. offers an "interpretation" of Jesus, it is precisely the historical Jesus who is presented to us--rather than distorting Jesus, or creating a figure, to express their own private perspective, their witness brings out the "real" significance of the historical Jesus. Thus Wright argues for a "critical realism" methodology. Next Wright argues for a common worldview of 2nd temple Judaism, via an examination of its typical praxis, symbols, and beliefs. Then he argues that we can best understand Jesus, the N.T., and the earliest Christian community against this background. In all of these arguments, Wright draws upon numerous extant Jewish sources and references to other scholarly works.
Wright's treatment is comprehensive, massive, detailed, compelling, and original. His treatment of Jesus, the N.T., and the early Christian community against the Jewish background brings them to life, is believable and convincing; and throughout his book he critiques other scholarly positions and demonstrates how his offers a more probable accurate historical point of view. In the process, he destroys numerous traditional critical theories and sets the direction for all future discussion.