Having said that, I do notice now that the liberal sexuality of the year 2130 is not completely enlightened. Although Captain Norton's crew includes numerous women, we still get a boob joke fairly early on, and perhaps more significantly all of the viewpoint characters (mostly Norton, but also members of his crew and scientists and ambassadors from elsewhere in the Solar System) are male. Clarke does his best to be race-blind - it's indicated that Norton has Chinese roots - but not talking about something isn't quite the same as making it go away.
It's interesting that the religious zealot on the crew is chosen to save them all from the missile sent by the ideological and paranoid regime on Mercury. Normally Clarke is not so sympathetic to religion, though of course the Fifth Church of Christ, Cosmonaut is in itself a parodic entity. I suspect that living on Sri Lanka, Clarke developed an appreciation for the spritual grace that can be gained even from rather odd theological systems.
Anyway, a classic that deserves its status.