Eternity

Here, from the other side of time, come:
THISTLEDOWN, the asteroid starship of a future that is not quite our future;
GAIA, a parallel reality where Alexander the Great's empire has ruled for two thousand years;

and

THE WAY, an infinite corridor through space-time which traverses and encompasses whole universes.
And as the strands of these mysteries are unravelled, so the ordering and the end of mankind -- and our entire Universe -- come into question.

Sequel to the classic space opera EON - a groundbreaking SF classic.