In need of a book suggestion

[Delicate]

I think the set of views he lays out is the most philosophically defensible picture of atheism on tap.

If someone wants to "understand atheism", or see a " worldview without God", the nice nihilism he describes is certainly intellectually defensible.

Once again you miss the point. A defense of atheism is a defense of the position that there is no credible evidence of god. Rosenberg does not do that. What he does do is present a single possible world view in the absence of a belief in god. In other words, he assumes victory in the battle Dawkins is waging over whether there is a god, and moves on to the philosophical questions Dawkins does not address. Whether you agree with him or not, he is addressing how to live in, and obtain knowledge in a godless world, not defending the view that it is indeed godless world. Humanism is another possible world view for a godless world. Neither is "the" atheist world view. There is no single atheist world view. And there are yet others.

Harris and Dennett address both questions: is there a god; and since there is not, how do we live in god's absense? They go on to address the third and fourth questions. What are te consequences of belief in god and how should atheists deal with those consequences?

Keep in mind I'm not just talking about atheism narrowly as a claim about the existence of God. Rather I'm referring to a whole atheistic worldview ( where I agree there can be more than one).

But as such Humanism is not a viable atheistic worldview.

What Rosenberg describes is pretty much the most viable view out there. And it answers exactly the question the OP asks.