Clever idea in the Time Traveler scene. You and your twin switch places with each swing of this time warping "pendulm". Lions and tigers and dinosaurs, Oh my! And the other way...warming and earthquakes and droids...Good Grief! Don't sweat the mechanics, just enjoy the ride.
I've enjoyed many of Silverberg's works, but this short book is more of a single idea than a finished story. In a CalTech time travel experiment, twin brothers are recruited for a time-travel experiment. Equally 'weighted' by their identicality, the time-travel gadget will send them swinging through time like pendulums, in an ever-increasing arc throughout history, each stopping briefly but separately at the same spots.
OK, it's not even much of an idea (the logical holes are obvious, as with most time-travel fiction.)
But there's no story. They do the experiment, it happens.
That's it. No plot, no tension, not even much character generation. No disasters occur, no revelations about the past or future are gleaned. So why read this book?
Silverberg is one of the very best sci-fi authors.
Goes back and forth in time.
This book is about an experiment in time travel...Like nothing I've ever read before. Twin brothers travelling in opposite directions in time, both at opposite ends of time i.e. one a hundred million years in the past, the other a hundred million years in the future. It's what they see as they're pulled back-and-forth by two singularities - a black hole and a white hole. Easy to read and very enjoyable.