“There's no place like home. There's no place like home.” Click your heels together and you're back in the sepia colored real world—but oh the magical adventures that were had! The Wizard of Oz is a well known pop-culture example of an Alternate World Fantasy, and it does a great job of showing one of the fully realized imaginative worlds that are created within the Alternate World Fantasy sub-genre.
Alternate World Fantasy is, just as the name indicates, a fantasy story told in a world other than our own—this could be a hidden world within our own, a parallel world, a different planet even. Journeys on other worlds are mysterious and invite adventure—indeed these stories tend to be stories of adventure.
There is a bit of a cross-over here with the science fiction parallel world subgenre, though the science fiction subgenre provides a scientific explanation/conceit behind the crossing of worlds.
World-building is a big part of any Alternate World Fantasy tale. Authors take great pains to immerse readers in these well developed worlds. It is worth noting that Alternate World stories also have a strong tradition in Science Fiction.
Variable. The level of magic is going to depend on the world created by the author. While Alternate World stories are mysterious and imaginative, magic is not necessarily a strong component of the world. Magic of some kind is almost always present, but really it's the fantasy of an alternate world that takes precedence.
Variable. By constructing another world, writers have plenty of opportunity for the exploration of social constructions and ideas. However, this opportunity is not always taken advantage of by writers, who may prefer indulgence in imagination (rather than getting bogged down in social commentary).
Moderate. World-building is the most important part of an Alternate World story, so sometimes developing characters takes a bit of a back seat. This is not to say that characters are flat or lifeless, just that readers will often get a break from them in order to see more of the fantasy world.
High. Plots of Alternate World fantasies tend to start in similar ways: a mysterious and magical world is found and the protagonist finds him/herself invested in it somehow. Adventure, journey, discovery, and mystery are all common elements of Alternate World plots and when woven together make for an active and engaging story.
Variable. The level of violence will depend greatly on the world created. The protagonist may be transported to a magical world and become its hero, doing battle to save a fantastical race of whatevers from devastation. The protagonist may embark on a more personal journey of self-discovery, with very little violence at all.
Urban Fantasy. A sort of sub-sub-genre, all Urban Fantasy stories are also Alternate World fantasies.
Portal Fantasy. Likewise, all Portal Fantasy is also Alternate World Fantasy. Portals to alternate worlds play a key role in the story—think mirrors, tornados, wardrobes, or other magical means.
Juvenile Fantasy. Fantasy for younger readers have gravitated toward this sub-genre because of its imaginative capabilities—infinite possibilities!
Crossworlds Fantasy. This sub-genre is part of the Mundane camp and its stories feature protagonists that are transported to another world where they must enter the fight between good and evil.
Most Fantasy is part Alternate World Fantasy because all have a vested interest in the creation of imaginative and fully realized worlds
By Lewis Carroll. A great example of the power of imagination, this story depicts a world within a mirror.
By John Myers Myers. A novel that draws its characters and settings from history, mythology, and literature this is truly a book for readers. It is a light and pleasant read with a classic storyline of stranger in a strange land.
By Roger Zelazny. An example of Alternate World where the alternate worlds are more of a mythic cosmology. The protagonists exhibit god-like characteristics.
By C.S. Lewis. A classic children's series that take place in the magical land of Narnia (though the existence of other worlds is implied). Magic, talking animals, and adventure are the feature of these stories.
By Philip Pullman. In this series readers are introduced to several worlds and the two main protagonists get separated and must travel between them in search for each other.
By Josepha Sherman. This book depicts a parallel universe that is also the land of elves.
By Diane Duane. This novel blends Fantasy, Science Fiction, and Cop Drama among seven alternate worlds where a conspiracy to 'cleanse' elves from the all the worlds is discovered.
By J.K. Rowling. This incredibly popular series is a story of an alternate world, a secret world of wizardy that exists within our own, but seems ever so vast.
By Barbara Hambly. A series that features two worlds separated by the void. The stories have dark magic, mystery, wizards, and a computer programmer. Get ready for adventure!
By Robert Holdstock. There are many novels and novellas in this cycle which take place in a forest that has been untouched since the last ice age. It is a labyrinth, a place of peril and living myths.