Just to be obnoxious...

may i suggest: Mammoth by John Varley (available in mass market) and at the library.

"Multibillionaire Howard Christian is one of the wealthiest - and
most eccentric - men in the country. Not content with investing his fortune and
watching it grow, he buys rare cars that he actually drives, acquires
collectible toys that he actually plays with, and builds buildings that defy the imagination. But now his restless mind has turned to a new obsession: cloning a mammoth." "In a barren province of Canada, a mammoth hunter financed by Christian has made the discovery of a lifetime: an intact frozen woolly mammoth. But what he finds during the painstaking process of excavating the huge creature baffles the mind. Huddled next to the mammoth is the mummified body of a Stone Age man around 12,000 years old. And he is wearing a wristwatch."--summary

Although multibillionaire Howard Christian can afford anything, he has one wish—to recover and clone a mammoth. To that end, he hires science professor Matthew Wright to find a way to repair his time machine and solve a particular anomaly from the distant past involving a frozen mammoth, a Stone Age human, and a wristwatch. The author of Red Thunder excels in imaginative sf adventure, bringing together an intriguing premise and resourceful characters in a tale of mystery, suspense, and a voyage through time.--Library Journal review