I'm Afraid You've Got Dragons — Peter S. Beagle

Dragons are common in the back water kingdom of bellemontagne, coming in sizes from mouse-like vermin all the way up to castle-smashing monsters. gaius Aurelius Constantine Heliogabalus thrax (who would much rather people just call him robert) has recently inherited his deceased dad's job as a dragon catcher/exterminator, a career he detests with all his heart -- in part because he likes dragons, feeling an odd kinship with them, but mainly because his dream has always been the impossible one of transcending his humble origin to someday become a prince's valet. Needless to say, fate has something rather different in mind . . .