Mathewson is repetitive and unconvincing in many areas. His conclusion regarding the various passages of the NT that seem to indicate a "soon" or "near" return of Christ is that while these indicate a hopeful expectation, they fall short of actually predicting that Jesus would return to earth within the lifetime of the NT audience. In other words, the statements that seem to assert a "soon" and "near" second-coming are really just reminders that the coming of Christ could be any time--imminent or delayed. As such, they didn't necessarily expect Jesus's return in their lifetimes, even if it was a legitimate hope.
Admittedly, some passages that Mathewson treats can be explained this way. He's also helpful in pointing out a tension that exists in some authors' writing that seem to indicate the possibility of nearness while expecting some measure of delay.
However, this means of interpretation doesn't seem to work in all examples, which makes Mathewson's exegesis quite strained in places. His refrain that, even after 2,000 years, it's still legitimate for Christians to say, "Christ is coming soon" rings hollow because it has, in fact, been 2,000 years since the writers of the NT made the claim and Christ hasn't returned. This leads me to believe that there must be better explanations for those passages that do not easily conform to Mathewson's explanation.