Analysis: What's Up With the Title?
If you've read to the end, you'll know that If on a winter's night a traveler unfolds into a longer sentence made of other book titles. That's why it's in sentence case, without all the normal capitalized title letters.
What's the sentence? Here it is, in all its glory:
If on a winter's night a traveler, outside the town of Malbork, leaning from the steep slope without fear of wind or vertigo, looks down in the gathering shadow in a network of lines that enlace, in a network of lines that intersect, on the carpet of leaves illuminated by the moon around an empty grave—What story down there awaits its end? he asks, anxious to hear the story. (21.20)
It's about staring down into an empty grave and wondering about how death is the same thing as the end of a story. Deep.
If you think about it, the "If" in particular makes the entire title completely speculative—something that exists only in the realm of potential, which is where all literature comes from.
Got that? Good.