Sometimes scientific advances are pushed into being by people who have no real interest in the science itself, but rather have an agenda of their own, often based on crass materialism, that drives the research as merely a sidelight to that goal. This book helps illustrate that point, as we find Howard Christian trying to develop a modern day version of a mammoth via DNA cloning, but in looking for source DNA material stumbles across not only a frozen mammoth, but a frozen man right beside it wearing a wristwatch and with a briefcase that just might be a time machine.
Howard hires mathematician Matt Wright, who has some new ideas in the area of time travel, to fix and/or duplicate that machine. Wright's investigation into the machine's operation eventually leads to a real trip back in time, for himself and Susan Morgan, an elephant handler who was hired by Christian to handle the result of the DNA cloning effort. The result of that trip, and the mayhem it does to modern Los Angeles, forms the balance of this story.
Each of the three characters is fairly well delineated, more than well enough to carry the story and drive the conflict. But there is a fourth character, a baby mammoth, whose story is told separately in interstitial chapters (styled as a young children's story), that actually may be the best portion of this book, as through this story the past of 15,000 years ago comes alive - the described environment, animals, climate, and behaviors of the mammoth herd all contribute to a sense of 'being there'.
Not so good is the basic plot, as it almost seems as if the story line was constructed with Hollywood in mind, with certain scenes just made for 'trailers', and too little work being done to really delve into the paradoxes that time travel (at the macro level) almost necessarily entails, even though such items drive the final resolution of the story. Varley has done much better in this area previously, and this work suffers by comparison with that earlier work and also in comparison to other works that have dealt with time travel, from Heinlein's "All You Zombies" to Asimov's The End of Eternity.
The net is that this is a good entertainment level novel, well written and engaging, with some good insights into the environment of the past, but has little to offer in terms of deeper meaning or any new twists on this type of story.
--- Reviewed by Patrick Shepherd (hyperpat)