Feist and Wurts (which, incidentally, sounds very funny together) put some major twists on the traditional "regular-person-pulled-into-a-different-world-that-he/she-is-destined-to-save" fantasy trope* in this story. Instead a plucky young pre-teen or teen, the character here is "Old Jake" a half-mad old wino whose only companion on a wet December night is Gran, an even older homeless woman that seems to be suffering from severe dementia. This is enough of a twist to make things interesting to begin with, but Feist and Wurts (again, funny) add the extra twist that Jake, for all the time that he ends up spending in the fantasy world he's pulled into, never really knows if it is real or just a vivid dream brought on by a cold, wet winter's night. This is in turn woven into the role he plays in the alternate world as "the doubter." By the end of the story, neither Jake nor the reader really knows if any of the events from the alternate world "really" happened, or is it was all in Jake's head.
Of course, I think that it isn't important to the story whether what happens to Jake is real or not. Instead, what's truly important is what it all reveals about Jake's character, about how he came to be homeless in the first place, and, more importantly, how he came to care so much for Gran. The story itself ends on a incredible down note, but not one that seems inappropriate.
*What I also like to call "The Narnia Plot."