I'm sure Niebuhr was a formidable thinker, and I see his relevance to some of the books I recommend in the article. But as I say in the article, that list isn't meant to be comprehensive. It's just a list of some thought-provoking books I've read that can spark a philosophical journey. I didn't read Niebuhr's book, so I couldn't recommend it. I've read some Berlin, but not much. In several articles, though, some years ago at least, I used his analysis of the two types of liberty.

The brokenness of humanity is indeed a premise that Christians can share with atheists. I call it the monstrousness of nature's mindless form of self-creation. Christians need a theodicy to account for that brokenness, given monotheism. Naturalists need cite only scientific models of causal relations.