The Island Snatchers

From the back cover of the DAW first edition: "Hibernia hijacked - Flying machines had not yet been invented on Earth's dimensional twin, Annwn. So Dylan MacBride thought it would be a good idea, even if a bit on the crackpot side from the viewpoint of that world's somewhat backward Victorian viewpoint. But when Dylan and his witch wife Clarinda tried out the machine by flying to Hibernia to attend a wild Irish wedding, they come a-cropper. For the Emerald Isle was not where it ought to be. Instead, it was drifting rapidly westward under some strange power. Now who would hijack a whole land of legends and fair lassies? And how was it done - and why? The Island Snatchers is a wonderful, whacky, and adventurous tale, replete with Little People, lost races, and super-scientific perils."