In America for the last few decades, Q discussions in America have been largely framed by scholars like Robinson, Kloppenborg, Mack and Crossan. In their works, these scholars claim, with a surprising amount of confidence, to know many things about the origin, development, genre, character, extent and purpose of Q. As a result, many far reaching conclusions have been asserted with regard to Christian origins and the historical Jesus. But truth be told, many of these conclusions have been built on little more than speculation and methodological problems are never hard to detect.
Let me try to summarize briefly the conclusions that have been drawn by many of the folks writing books about Q who have based their works on the above-mentioned scholars. It is frequently assumed (and occasionally argued) that Q was once a single Greek document, or that it can be precisely classified according to genera (e.g. "sayings of the wise") or that Q and the "community" responsible for it can be fairly associated with ancient Cynicism. Early Christianity, we are told, began with a group of itinerant Cynics who liked to talk about nature and who enjoyed being a stick in the eye of traditionalism (earliest strata of Q). Afterwards, it evolved into an eschatologically-oriented group with much closer ties to Judaism (later strata of Q). Then, with the composition of Mark's Gospel and with the stratified Q's eventual enshrinement in the Gospel's of Matthew and Luke the origian Q was lost and all but forgotten ... until recent scholars recovered it and explained to us what it all means.
Kloppenborg's stratification theory and Downing's, Vaage's, Crossan's and Mack's claims about Jesus being a "Cynic sage" have provided popular authors with fodder for all sorts of ridiculous historical reconstructions about the life of Jesus and early Christianity. In his own historical sketch of Q research Casey runs through the scholarship leading up to our sad current state of affairs in Q scholarship, focusing on men like Toedt, Luehrman and Kloppenborg, showing how their methodologies were very unsound and have been accepted all-too-uncritically. Casey complains of how Q research has become "beaurocratized", by which he means that scholars often rely on one another's prior arguments rather than personal examinations of the primary source material (e.g. the recent discoveries at Qumran). He also points to the way arguments for Q involve a lot of question-begging techniques. For example, the arguments Kloppenborg uses to show how Luke or Matthew displaced certain sayings within Q could just as easily be taken to show that these sayings originally existed independently and were not extracted from an existing document (at least not one with its own meaningful arrangement) and then rearranged according to the redactor's theological programme.
Casey's criticisms on recent Q scholarship would alone make the book worth buying since good criticisms like his are going virtually unheard in the ruckus of all the sensationalist ideas being proposed these days.
Casey also, rather unexpectedly, criticizes many of the early Aramaic approaches to the Gospels, even Matthew Black's impressive work. I found his remarks here insightful and an indicator of his own reflective and critical mind.
Casey's thesis is that at least some of Q was originally preserved in Aramaic, not Greek. Moreover, it was not a united composition, but may have existed as several independent sayings. The translated Greek Q existed in at least two translations before Matthew and Luke got to it and these distinctive translations are detectable and partially recoverable by retroverting the texts into Aramaic - the language in which they were originally preserved and which Jesus most likely knew and spoke.
Casey also challenges the widespread assumption that Q contained nothing more than what Matthew and Luke now hold in common. For example, it is often characterized as a "sayings source" since it contains very few narratives. But this claim relies on a rather elaborate view of stratification. As it comes down to us, Q contained several narratives (e.g. stories about John the Baptist, Christ's temptation, the healing of the centurion's servant, Peter's leaving the scene and weeping bitterly after his three-fold denial, the question posed to Christ, "Who is he that struck you?").
One problem I have with Casey is his method of demonstrating the Aramaic Vorlage behind Q: he tries to show how Matthew or Luke may have misread or misinterpreted certain Aramaic words. I'm not convinced any of these arguments really hold up.
Still, the book comes as a refresher to me since I've read several books on this topic now and they've usually been from the same standpoint. This book offers a different look at things and I think presents some good food for thought. A more comprehensive book on Q that I'd recommend is "Q and Early Christianity" by Christopher Tuckett. Richard Horsley has also written some good critiques of Kloppenborg. For a good critique of the Cynic hypothesis, Craig Evans has a good chapter in his book "Fabricating Jesus." It's a very easy read too, unlike this book by Casey.