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.
