The upshot of this is that my only objection about the book, namely that it shifted uncomfortably for me from allegory to magical realism, is actually completely misplaced (or arguably so; another outcome of our discussion was me realising how rigidly I interpret what I read). When I started reading the novel, this is actually what I thought was going on, but I shifted by the end when my brain gear-shifted into neutral. So much my fine reading and analytical skills (though I did only get a 'B' in Higher English). Anyway, all of which serves only to further elevate the book in my estimation. Whew, I got there in the end.
Changing the subject (and drawing a veil over my shame), one thing that C and I did agree on was a certain disconnectedness between the novel's tale of the Tiger's Wife from its other narrative strands. Natalia's story, as well as her grandfather's interludes with the deathless man, revolve around mortality and war. While the tale of the Tiger's Wife isn't devoid of these elements, it's a bit of a leap to tie it in so well. Which isn't to say that it's not an important part of the novel's strengths, just that neither of us entirely got it.
We did disagree somewhat on the novel's various detours. C (and some of her book group) thought these were a little too tangential to the main narratives, and almost seemed short story-like in their drifting away from Natalia and her grandfather. It's merely a matter of opinion, of course, but I didn't feel this way at all. Instead, I thought that what seem to be digressions (often lengthy ones) are actually quite important for setting up the characters prior to the roles they play in the main narratives. So knowing, for instance, of Luka's failures in a distant city makes his behaviour towards his wife comprehensible (if still repugnant).
Anyway, we had a great old discussion, and it was good to be set straight. I'll be sure to read more carefully in the future!