As I sit here editing an interview and dodging doing any of my own writing, I find myself pondering the subject of magic.
Once upon a time, being a smartarse, I replied to a thread on overused things in fantasy with the answer 'Magic'. That was part me showing my irritation at that sort of question, but part genuine answer. It is very very difficult to find a fantasy book that does not feature someone practising magic at some point. There is no shortage of fodder for fantasy novels out there that don't involve anyone casting spells at all.
Nevertheless, magic does dominate the genre's imagination. A new "Help me with my magic system" thread pops up on my various forums every week or two. People often recommend books partially due to their innovative new magic system. Many an author has chimed in with their thoughts. Those I've read tend to focus more around magic's use as a plot device and unique fighting style, which judging from the aforementioned threads, seems to be very helpful advice to many.
For my taste though, this leads to an overly narrow and unholistic view of magic in the genre. I would like to see more advice and more thought on how to use magic as a setting detail.
I would stress straight away that I cannot think of a single author who doesn't embed the magic into their setting in some way. The more you think about it, the more you can see what they've done. But you do have to think about it and it is uncommon, in my experience, for it to go deep. I think authors are doing themselves a disservice by doing so because vibrant settings make for vibrant books and the deeper any setting detail runs, the more vibrant the setting is.
I think a great example of this is The Wheel of Time. Its arguably one of the classics of the genre and in a lot of ways you have to ask why. Few series attract as much internet teeth grinding over characters and plot. It would be remiss to suggest that there isn't a great deal of love for the characters and plot (often from the same people) but it clearly overcame many flaws to hold its position. If you compared WoT to many of its peers, one of the things that stands out most clearly is the quality of the worldbuilding. That goes for the One Power as well. History of its use, different philosophies, social status of users, its effect on history - its all there. Trying to imagine WoT without the One Power is like trying to imagine it without Rand.
Another example would be Tigana, again an arguable classic (and certainly an internet favourite for best stand alone). There are very few stories where magic is more central to the plot but it runs deeper than that. Every culture has its own magic and practices, as well as their views towards its use. It forms part of their deepest, oldest myths. It forms part of their heresies, their politics, their everything. And Tigana isn't even a magic heavy book - not next to Mistborn or WoT. Just there's a few really well placed bits of magic and the ramifications are everywhere.
There's some common threads here at a quick look -
If magic is truly part of a setting, then it should be part of its history and its pre-history.
Views on magic should vary by culture. Even in worlds where believing in magic is like believing in the kitchen table, differing histories and philosophies will lead to divergent views on magic, just as there's divergent views on how to eat your dinner.
Usage of magic should change too. The closest equivalent to magic in terms of real world history is probably military technology, and the most cursory inspection of the history of said reveals continuous difference in usage.
And it should have a place in the power structure. Power has always found its way into governments somehow. If practitioners are not involved, then there must be a reason.
I would add a final thing that's sorta there, sorta not, but in any case, something I really like to see -
Fantasy worlds with acknowledged magic should see people with very different views on life, death, the sacred and everything else to those of this planet. This is most pronounced with D&D-esque worlds where cheating death is relatively straight-forwards (if difficult) and where its entirely possible to summon angels and ask them questions about the gods, but even in low magic worlds it should be making a difference.
Maybe people would view it with the same matter of factness they treat the technological advances of today. Maybe they'd react with the violence of the Luddites. Maybe they would view it as inherently sacred and spiritual. Maybe we'd get people taking the philosophy of magic and applying it to their everyday business, like people do with Sun Tzu. But there should be something. The miraculous and other acts of genius change the world. Worlds - even imaginary worlds - that don't change are stagnant.
And vibrant worlds sell books.