Alan Dean Foster 
Candle of Distant Earth 

Marcus Walker, a former hotshot commodities broker, and a wisecracking dog named George, who has been speech-enhanced to increase his market value, have escaped their alien Vilenjji captors, who saw the two as cuddly extra-terrestrial "pets" to be sold for a hefty sum. But Walker hasn’t a clue which way will lead him back home to Chicago. With the Vilenjji hot on his trail, Walker must pull off the impossible and pinpoint his needle of a solar system in the universal haystack. Will the unrelenting Vilenjji get to him before he reaches Wrigley Field? Yep, it’s a wide-open universe out there, bursting with possibilities – and Walker’s going to get hit with all of them.