Epigraphs are like little appetizers to the great entrée of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
The Cost of Living
Go then, adventurer, on your vivid journey,
Though once again, of course, I cannot join you—
That is as certain as your happy ending.
The one-armed captain in the pirate harbor
Would know me in an instant for a Jonah.
No gnome would ever speak with me for witness,
And so let slip the spell-dissolving answer
Before you'd even heard the sacred riddle.
I, as it happens, know it from my reading,
But the blind queen would ask it in a language
Not the syllabus of my old college,
But which your loved, illiterate nanny taught you.
No, I will stay at home and keep things going,
Conduct the altercation with the builders,
Hoe the allotment, fix the carburetor.
I'm genuinely happier with such dealings;
It isn't merely that they pass the seasons
Until I hear your footstep on the threshold.
Then I will sit and listen to your story
With a complacently benign amazement,
Believing it because it's you that tell it.
And when you've done, and I have asked my questions,
I for the umpteenth time on such homecomings
Will say what's happened to the cost of living.
What's up with the epigraph?
Just like the narrator telling the story and writing this epigraph, we can't literally go on the journey into the Empire, much as we might want to. We can observe from afar, but we can't dive into the book and directly participate in it its magical adventures—just like the narrator:
The one-armed captain in the pirate harbor
Would know me in an instant for a Jonah. (0.4-5)
Do you know what the narrator means by "a Jonah"? Jonah is a dude from the Bible. And by a dude from the Bible, we mean a disobedient dude. Long story short, when someone is called "a Jonah" it basically means they're bad luck—because Jonah brought a giant storm to a bunch of innocent sailors all in the name of shirking his calling. The narrator's calling, it seems then, is to let the adventure unfold without meddling in it.
While it's fine and dandy for the narrator to mill about his or her home doing chores and such, what really piques our interest in this epigraph is the question of whom the narrator is addressing. For a story that unfolds in the third person, it seems pretty significant that the epigraph is done in the first person—and from the perspective of our narrator instead of our protagonist.
While it's tempting to assume that the narrator is addressing us—we are the readers, after all—we think they are actually addressing Tilja. Check out this bit:
Until I hear your footstep on the threshold.
Then I will sit and listen to your story
With a complacently benign amazement,
Believing it because it's you that tell it. (0.18-21)
It sounds like our narrator is waiting for someone to return from a journey, right? And while we certainly finish a journey when we complete the book as readers, our trek pales in comparison to Tilja's. Plus, we're not about to tell anyone the story we just read is true—but Tilja would. And it sounds like the narrator is poised to believe her.