Rieser covers the motives of the Diaspora Jews and then the Hellenes in creating the Christian myth-system. Historical Jesus scholars assume Christianity began in Palestine and spread from there. They put their theoretical feet too firmly in Palestine, when Christianity was actually a product of the Hellenistic urban world, which somewhat violently took over the old, thus respectable, Jewish scriptures to give credibility to the new, Christian religion.
Rieser has his theoretical feet firmly planted in the urban Roman empire, with an emphasis on my favored period of 70-313 CE, with a bit of focus on the pivotal change after that as the Christian religion became officially accepted and then co-opted and mandated by the same kind of power hierarchy it was originally designed to resist.
Rieser recommends we study the detailed socio-economic realities of Palestine as a backdrop for religious, pseudo-historical, edifying political fiction. He shows how Christianity was started by the Jews of the Diaspora. It was soon taken over and fully Hellenized by the lower class throughout the Roman Empire (with an increasingly artificial Jewish veneer).
Christianity arrived last, not first, in Palestine -- that's why Christian archeological finds appear in Rome but not in Judea until the fourth century. Jesus, the Apostles, and Paul are entirely fictional, though loosely based on types of actual individuals. Christianity was initially started by Jews, though these were the very heavily Hellenized Diaspora Jews, not the less-Hellenized Jews in Palestine.
The heavily Hellenistic communities gradually invented and pulled together the pseudo-historical single figure and retroactively set him into the pre-70, Palestine backdrop.
Once you abandon Historical Jesus -- and Historical Apostles and Historical Paul and that whole way of thinking -- many superior theoretical options open up for understanding the early Christian religion in terms of a mythically allegorized socio-political counter-religion to the hierarchical honor-hyperinflating system of divinized Caesar. (I would point out that it also opens up the researcher's ability to think of earliest Christianity in terms of mythic allegory that describes and conveys primary religious experiencing.)
Christianity was almost immediately co-opted by the gentile lower class of the large cities of the Roman Empire, especially Rome, Alexandria, and the cities of Asia Minor (just to the east of Greece, including Byzantium/Constantinople), with increasing animosity between the Hellenists and Jews. The Hellenist lower class found the Hellenic transformed version of the Jewish Diaspora messiah religion to be useful politically.
When Christianity finally arrived in Palestine, the Jews there shunned it as alien, unfamiliar, and just another attempt to invade and corrupt Israel with Hellenism.
Rieser mentions the central importance of sacred meals in mystery religions and mentions Jesus as the "drug, or pharmakos, of immortality", but has no insight into entheogenic experiential allegory. Why would wine and bread deserve to be placed at the center of any Hellenistic religion? Historical and socio-political treatments such as this tend to completely omit religious experiencing from their theory of Christianity.
They assume that the ritual makes the eucharist or sacrament seem potent, rather than vice versa. Though Rieser explains how the Hellenized transformation of the messiah story was politically meaningful and useful to the Hellenes, he doesn't mention that it was also fully amenable to allegorically expressing the standard core mystery-religion with a storyline that is fictionally set in Palestine rather than in the mythic realm as such.
Instead of a story about a mythic Prometheus chained to a rock, or a mythic Attis tied to or encased in a tree trunk, or Isaac bound to the altar, the pseudo-historical Jesus figure is fastened to a cross, just like (as Rieser states) the actual rebel slaves and underclass in Rome or in Judea.
Rieser has only passing, shallow coverage of the mystery religions. But if the Hellenistic mystery-religion mythic storylines were intended to describe the initiation experiences encountered by the mystery-religion initiate after consuming something sacred, the pseudo-historical Jesus storyline may also be experienced firsthand after the Christian initiate partakes of a Last Supper before entering the kingdom of God that is revealed when time ends.
Rieser provides plenty of hooks for such an explanation, but, like almost all the overly historical-oriented modern researchers, is unable to treat this experiential allegory dimension which calls out for coverage.
Rieser reduces religion to the socio-political realm instead of recognizing the overlaid, richly interpenetrating layers of political allegory and mystic-state experiential allegory. The mythic-only Christ theorists Freke and Gandy, conversely, explain experiential initiation in the original Christian religion, in The Jesus Mysteries, and in Jesus and the Lost Goddess, but omit the socio-political layer of allegory.
The socio-political perspective without mystery-religion experiential allegory is less than completely convincing, because it implausibly omits Hellenistic-style primary religious experiencing from early Christianity.
Rieser's plausible and realistic view of the Roman Empire and the changing Hellenistic/Jewish relationships is still ahead of current research in the U.S. Every Christian-origins scholar should read The True Founder of Christianity and the Hellenistic Philosophy. Its style, perspective, and sensibility are valuable and it makes an essential contribution to the field.
I have read The Jesus Myth, The Jesus Puzzle, The Jesus Mysteries, Deconstructing Jesus, The Christ Myth, The Christian Myth, and The Christ Conspiracy. See also Rieser's book Messianism and Epiphany: An Essay on the Origins of Christianity.