Ashley Capes shared an interesting take on “soft” magic systems today. http://mythicscribes.com/?wysija-page=1&controller=email&action=view&email_id=12&wysijap=subscriptions&user_id=712. I’ve had discussions on this in the past, including a rather interesting Twitter exchange with Nat Russo. While in general, I hold to Branden Sanderson’s First Rule of Magic, which is never have a PoV character use it without explaining it, it’s important to qualify that even there, he is talking about the Point of View character.
And even there, he’s quite willing to change the rules, let them learn things piecemeal, or just be flat out wrong on issues. See Kaladin in the Stormlight Archives. Neither he nor Shallan actually have much of the picture with regards to what they’re doing. And they learn more all the time. He did the same thing in Mistborn. So he’s certainly not adverse to having characters surprised by magic.
And I think that’s important. Especially if you have a character that doesn’t use or understand magic. Why should the reader inherently know more than the people living in the world? Let people be surprised. Let them learn by doing and interacting. Even when some things appear contradictory.
Contrary to the article, I don’t think this is a ‘market’ issue. It’s an issue of good storytelling. Whether you mean magic, tech in Sci-Fi, or high-stakes finance in a political potboiler. The rules the characters live under need to be explained as they’re encountered, to the extent they understand them. No more. No less. Neal Stephenson can get away with dropping an author tract that no one but ten people understand because he’s funny as Hell when he does it. But if your name is different from his, don’t get wrapped up in minutiae they haven’t seen. Let them explore, learn, read, and conjecture with the characters.
That’s what Speculative Fiction is about, at its heart, after all. The sense of wonder at finding the unknown, entering a new world and dwelling in it with the characters.