There's much discussion of orbital mechanics, disguised as a story. The rest isn't as good.
OK, actually I rather enjoyed it, but only because I'm a sucker for apocalyptic fiction and hard-ish science, and I gave immense credit for the chutzpah of his opening sentence, in which the moon explodes for no reason.
I found his treatment of religion more annoying than usual for sci-fi. His atheist wish-fulfillment fantasy "then everyone realized there's no God" is par for the course. Projecting thousands of years of human development without belief in God recurring, and with no other apparent solution to the meaning of life, is sloppy but also usual. What really grates is the ending, which reveals that — surprise! — people do care about having a supernatural purpose and, oddly, a powerful cabal has found one but they're keeping it secret. It reminded me of Contact where after relentlessly bashing religious rubes, at the very end Sagan reveals that the universe has been designed by, if not God, something seriously God-like. I find their lack of faith in lack of faith disturbing.