The following is an excerpt from an article in the New York Times:
No poet of our day has such a well-earned reputation for difficulty as the Englishman Geoffrey Hill, and there are few whose moral vision is so imperiously unsparing. Of late, however, the almost belligerent demands of Hill's severe and densely forbidding poetry have taken an improbable turn: part of what's become daunting about his work is simply keeping up with it all. ''The Orchards of Syon'' is Hill's fourth book in six years -- an ample output even for poets of sunny disposition, but for one of Hill's penitential austerity over the previous 50 years, it is something closer to a mutinous outburst.
I don't understand the sentence in bold. I've looked up the words one by one in the dictionary. But I still don't understand. Can anyone rephrase it with more accessible words?