O'Regan pointed to the "exile" of apocalyptic in the modern period, and its "contemporary return" in a host of theologians, including, but not limited Hans Urs von Balthasar, Jurgen Moltmann, Johann Baptist Metz, Sergei Bulgakov, Karl Barth, Stanley Hauerwas, Jacques Derrida, (to a limited extent) the Pope Benedict XVI, David Bentley Hart, Catherine Keller, John D. Caputo, and Gianni Vattimo. Apocalyptic is not so exotic before, especially since we find such diverse thinkers sharing the same theological "spaces" (e.g. Balthasar, the "Pope's theologian," and Derrida, share the same space - this is surprising) O'Regan finds it helpful to map out three spaces in order to distinguish these different thinkers. He has three of 1) maximum level of content; 2) in-between level of content; and 3) empty of content.
I took a course in Fall '10 on apocalyptic and theology. This little book was set as a second reading for the last week; and nobody read it, mostly I'm guessing because it's got such a scary title. It's really a shame, because O'Regan cogently summarizes much of that course's syllabus. There is a constructive argument in here, and an interesting one, but in its way this is really a short reference work and a darned useful one. For a compression this quick and effective of such a potentially sprawling topic, four stars is no exaggeration. I expect to return here as I put together at least one of my exams, and probably two. (O'Regan catches the connection between apocalyptic and pneumatology a couple of times, which is very astute.)
For the record, our thinkers, with O'Regan's categories: Pleromatic (i.e. the apocalypse has content, and we can and do know it)-- Moltmann, Bloch, von Balthasar, Bulgakov, Milbank, David Bentley Hart Kenomatic (i.e. the apocalypse is the end of all content)-- Derrida, Benjamin Metaxic (elements of both those logics)-- Altizer, Keller, Metz
If you're a theologian of the younger generation, you probably smell a good ripping fight or three brewing just looking at those categories. O'Regan even starts a few of them for you. I was left wanting to reread Benjamin and consider (again) where in heaven's name you even start with von Balthasar.