Happy endings are hard-earned in Owen Parry’s ”American Christmas Stories,” and gifts don’t come in tidily wrapped packages. If you’re really lucky, you’ll be rewarded with a lump of coal. That’s what one secret Santa (a bighearted, small-town Pennsylvania cop) delivers to freezing, out-of-work miners in the 1887-set ”Coal & Iron.” In ”The Christmas Joe,” a Depression era waitress gets a baby — and the Virgin Mary she ain’t. Parry has an almost Dickensian eye for detail, and a light hand with religious themes. Also in Strike the Harp!, irreverently playful poems — tweaking the three kings, holiday shopping, and more — punctuate each short story.