Billy the Kid was famously slain by Sheriff Pat Garrett at the age of 21 in New Mexico and became an icon of the West. But legend has it that his parents were Irish immigrants from the slums of the Bowery in New York City. Michael Wallis (author of "Route 66" and "Pretty Boy") does his best to separate fact from fiction in "Billy the Kid: The Endless Ride." Wallis, incidentally, is quite an interesting character: he hosts the PBS series "American Roads" and has done voice work for Hollywood films such as "Cars." ($25.95 / 288 Pages / W.W. Norton)