Ludmilla is a sneaky one, isn't she? At first, she seems to just be the love interest for you, the person assumed to be a straight male reader. But throughout the course of the book, you discover that she's implicated in some huge book printing scandal. Don't tell us you were expecting a straight-up romantic plot…
In If on a winter's night a traveler, you're after two things: the books you've started reading and Ludmilla. At one point, Calvino even steps in and makes this connection for you:
You are bearing with you two different expectations […] the expectation contained in the book […] and the expectation contained in [Ludmilla's] telephone number (3.34).
For Calvino then, your approach to the unfinished books is very similar to your approach to Ludmilla. And when it comes to both, this book plans on knocking you down a peg or two.
You want to possess both the books and Ludmilla because to you, both are always dancing just out of your grasp. Just as you can't finish any books, you can't seem to "know" Ludmilla in any final way. Each time you think you've got her figured out, Ludmilla tends to say something that you don't really understand.
In fact, the best chance you get as the Reader to "know" Ludmilla comes from the impressions given off by the things in her apartment. "Observing [her] kitchen," for example, "can create a picture of you [Ludmilla] as an extroverted, clearsighted woman, sensual and methodical; you make your practical sense serve your imagination" (13.11). Oh yeah, did we mention you've become Ludmilla in this moment?
Ludmilla is a private person, but she does not mind when men she barely knows come and go from her apartment. Bottom line: she looks at the world in a way you don't really understand. The book, though, really wants you to get there, since Calvino ultimately likes Ludmilla more than you.
Sorry, but it's true.
Just like you (Calvino's you, at least), Ludmilla is mainly characterized through the approach she takes to reading. You probably noticed that time and again, you (the character) are confronted with other characters whose styles of reading are criticized. But the book never celebrates your "normal" approach as an alternative. Instead, it holds up Ludmilla as its ideal reader.
Why? Well, in contrast to your straightforward expectations for interesting characters and a clear plotline, Ludmilla comes to books from a position of almost total innocence. She wants books to be organic and full of wonder, just as she wants to read authors who produce books "as a pumpkin vine produces pumpkins" (15.107).
Remember when Ludmilla refuses to join you on a trip to the publishing house? When you press her for a reason, she claims that "There's a boundary line: on one side are those who make books, on the other those who read them. I want to remain one of those who read them" (9.30). This woman wants to think of books as things full of magic and potential; she doesn't want to be exposed to all the nitty-gritty, behind-the-scenes business stuff of publishing houses.
To emphasize Ludmilla's awesomeness when it comes to reading, Calvino juxtaposes her with her sister, Lotaria, the stuffy academic. This is a woman who seems to read books "only to find in them what she was already convinced of before reading them" (15.83). Oh, academics. Ludmilla, on the other hand, reads books with an open mind toward the many different kinds of pleasure they might offer. That's more like it.
Every other character in the text, in one way or another, has a set agenda when they approach a book. Calvino wants us to throw that all out the window and, instead, learn a little from Ludmilla's example.