The Doctor and the Kid — Mike Resnick

Welcome to a West like you've never seen before! With the O. K. Corral and the battle with the thing that used to be Johnny Ringo behind him, the consumptive Doc Holliday makes his way to Deadwood, Colorado. But when a gambling loss drains his bankroll, Doc aims for quick cash as a bounty hunter. The biggest reward? Young, 20-year-old desperado known as Billy the Kid. With a steampunk twist on these classic characters, nothing can be as simple as it seems.