Our Alternative Universe

A day with family (lift to Aileen, breakfast and walk with Sheila, lunch with Ketlan) prevents posting but can generate material for later posting (watching His Dark Materials with Ketlan).

A fictional narrative can:

be set in our universe;
be set in an alternative universe;
involve travel between alternative universes.

I suggested here that four stories by Poul Anderson could be republished in one volume because they present the following sequence:

an alternative history;
travel between alternative histories;
a meeting place between the alternative histories.

SM Stirling's Draka Trilogy shows the (dreadful) Draka Race conquering Earth in an alternative history whereas the same author's fourth Draka novel shows them failing to invade and conquer our Earth. 

What seems to be "our universe" can also be seen as an alternative universe:

Thus, every work of fiction is set in a timeline that differs or diverges from the timeline inhabited by its readers. It follows that every work of fiction is set in an alternative timeline even though we do not usually have any reason to think of them in this way.
-copied from Fictional Timelines.

In any case, if there are many parallel universes, then our universe can be seen as just one more:

"I hated that history, its filth, its waste, its ugliness, its restriction, its hypocrisy, its insanity. I will never have a harder task than when I pretended to be an American..."
-Poul Anderson, "Eutopia" IN Anderson, Past Times (New York, 1984), pp. 112-141 AT p. 125.

Three similar examples from visual media:

when a comic book supervillain reported that there was one Earth where no one had gained any superpowers, another villain retorted that that sounded unlikely...;

superheroes written by Alan Moore ended an issue by arriving on an Earth that was visibly darker and grimmer than theirs...;

in His Dark Materials, one character, stepping through an invisible gate, disappears from the alternative Oxford and arrives on a street where the crowds, their clothes and the passing vehicles, including a red double decker bus, are all too familiar to the TV audience...