It's almost 18 years since I went to college, which as a side note means that soon MrsDarwin and I will have known each other half our lives. Not a bad thing, that.
We met at a Freshman dance and ended up talking till two in the morning. I don't recall exactly how it came up, but the moment when I realized we were going to be friends was when she said, "We could go over to the student center and talk for a while."
I replied, "Of shoes and ships and sealing wax?"
And she responded "Of cabbages and kings."
I'd come up to college with the conviction that probably the best indicator of whether someone was a worthwhile friend was whether they liked the same books. If someone liked Tolkien and Lewis, we were clearly going to get along. If they expressed a distaste for science fiction and fantasy (about which I felt strongly enough at the time that I was convinced it was an indicator of seriousness whether you knew to talk about SF rather than SciFi) they probably weren't worth knowing.
I'm not entirely sure how I got to thinking this way. My parents' set of friends mostly went back to their college days and they all shared an interest in Tolkien and Lewis, and in science fiction and fantasy more generally, but my parents themselves were not as exclusive as I, in my youthful enthusiasm, was.
The reason this is particularly strange for me to look back on is that in the ensuing eighteen years I've not only ceased to see shared interest in genre fiction as the primary indicator of intellectual commonality, but I've almost entirely stopped reading science fiction and fantasy. Looking back over the books I read this year, I read 26, of which 4 were science fiction or fantasy. Two of those were by my sister, and the other two were re-reading The Fellowship of the Ring and reading Andy Weir's near-future SF novel The Martian.
I think a part of this is that it wasn't till I got out and had a wider experience of the world that I began to realize what I had got out of favorite books was not necessarily what others got out of them. There are a lot of people who love Tolkien's books who get very different things out of them than I do, and love them for very different reasons. And just because I found beauty and truth in Tolkien's novels does not mean that people who aren't particularly interested in Tolkien have no interest in beauty and truth. Of course, this was deeply faulty logic, but one often barely thinks about these things consciously. Instead, one has a sense of what accounts for "like me" in some basic way.
Friendships tend to be sparked by some sort of commonality: intellectual interests, work, parenthood, religion, politics, living next door to each other. It's probably best to have friendships rooted in all these different areas, and to one extent or another I suppose I do. Even among friends who are also book people, as I've become less dogmatic in my reading tastes, I now number among my friends people who simply don't like Tolkien or Lewis. It does work.