As humans we like to create classifications. There are a few good reasons we do that. It helps us get an immediate picture of what to expect from a thing; identify other, similar things; and decide whether we want it. We apply this to principle  to books as much as to fruits and televisions.

But there is a downside. Using “fantasy” as a search term quickly reveals a number of books we might not care to read, so we have developed finer distinctions, more subsets, to help us locate those we do. The possibilities for new categories are endless. We now have epic, historical, low, high, urban, dark, contemporary, and military fantasy, among others. But with so many separate classifications, we begin to lose sight of the common spirit we saw and liked in all of them.

An SF author’s job is to grab hold of that spirit and  create something new. You may end with a book that seems like fantasy, but is actually up to its eyeballs in high tech and aliens (Gene Wolfe’s The Book of the New Sun) or one that reads more like Jane Austen (Ellen Kushner’s Swordspoint). The intent is not to confound someone looking to simplify his book search, but rather to offer that person something new, and also something old; the imagination and boundary-testing that drives the SF genre.

The cross-genre books are the boldest in this regard, but it can be found in all good fantasy books. An author who reliably stays within her category can challenge your perceptions or beliefs in some way. It could be subtle, or it could fall on your head with the weight of a thousand coffee mugs, but it will likely be there. The cross-genre books stand out as symbols of what is possible and how far it can go, but in that sense all good books are the same.

There are those who will read only hard science fiction, or only paranormal romance; that’s fine. I won’t argue that categories should not exist. I will argue only that they are not always helpful. When there is a story that doesn’t quite fit into a slot, it could become popular and give birth to a whole new category—or it might meet with confusion, as readers wonder what it is and whether they might really like it. This goes for mixing the smaller subsets of a genre as well as mixing the genres themselves. Teresa Frohock’s Miserere seems to have met with an undeserved wariness from buyers, with some calling it religious fantasy and others calling it dark, and few finding a label that fits. But if SF is meant to challenge our preconceptions and push us out of our comfort zones, why are we so hesitant and discriminating?

Cross-genre books are a natural outflow from the creative mind, a natural result of the adventurism of SF—born from the same impulse and driven by the same curiosity. We should read them because they are inspiring and risky, but we should also read some of the quieter books that approach the edges in more subtle ways. Cross-genre books aren’t the  only books that can get us to that new place, that new question, but they do remind us that’s where we want to go. Too much attention to categories might distract us from getting there.