Josephus as Historical Authority?

I recently picked up Steve Mason’s book Josephus, Judea, and Christian Origins: Methods and Categories and found this introductory statement to be interesting.

“The following study addresses what seems to me a fundamental problem in the use of Josephus’ writings for studying Roman Judea, namely his status as an authority. I begin from the observation that Josephus is, and has always been (though for changing reasons), regarded as a peerless authority for first-century Judea, and this assumption runs even more deeply than we perhaps realize. My argument, simply, is that he should not be so regarded. This is not because he is unworthy or ‘unreliable’ or only partially reliable—or because of anything to do with reliability. It is rather because the whole appeal to reliable authority in the discipline of history is an error of categories. History has, or should have, a problem with authority” (Steve Mason, Josephus, Judea, and Christian Origins: Methods and Categories [Peabody, MA: Hendrickson, 2009], 7). I am not sure that I agree with Mason, and I know this is not his main point, but I find it annoying that whenever Josephus and the Gospels or Acts appear to be in conflict regarding a historical matter, Josephus is usually treated as sacrosanct. I have argued that this is not good historical method.