In the course of my moving in with him in January, The Boy (who I think needs a new nickname) & I combined our book collections. Gasp! I know. My friend K. and I always talked about how that is the true measure of committment, never mind rings, pets, or mortgages.
At the time, we thought that we had just two duplicates in our entire collections - The Things They Carried and The Catcher in the Rye.
However, in the course of moving into the new place, he did a more exhaustive survey. And we found that in the category of sci fi & fantasy, we ended up with six duplicates - most of which issue from the realms of Tolkien. And so, to commemorate this fact, the moving box that housed all of our combined sci fi & fantasy received the Sharpie-d title, "CAUTION: This Box Contains Pure Nerd." ;)