I first read this book when I was 12 or 13 and it definitely had an effect on me. I think part of it was the not quite human protagonists. And certainly the exploration of deep time is something. It’s on par with Larry Niven’s Ringworld or Frank Herbert’s Dune when it comes to world building. And at just over 400 pages, Robert Silverberg crams in a grand scale adventure without a lot of wasted pages.
The story is about a band of chimp-like ‘humans’ who emerge from a protective cave system (called the Cocoon) after many thousands of years. They fled below the surface when the planet was bombarded with meteorites, causing it to become unlivable. You soon realize that this story is set somewhere far in the distant future of our Earth. The world they find is changed and not quite what they expect. And as they learn more, they find some shattering truths.
Silverberg expertly juggles a large cast of character, an extremely complex and fleshed out culture, and an epic tale of discovery. This is an author at his height. It surprises me that this book is not more widely read and talked about. Fans of good stories told well should seek this one out. Grand, epic visions like this, told in a compact and efficient way, are far too rare.