Good and bad magic
Here's what's annoying about fiction dealing with magic: if it's not laid out with proper rules, or the rules aren't followed, it's nothing more than nonstop narrative cheating. I read a trilogy lately in which magic played a small then larger then important part, and each book got less satisfying as the role of magic grew. Why? Because it could have been anything at all. The more the plot depends on some arbitrary performance of some arcane ritual never mentioned or described or costing anything, the less the success means. It robbed the payoff of any weight. The same goes with the time pressure writers like to put on magic, too. Someone must perform some long and complex ritual! How long does it take? Just a little bit longer than we'd like, but it gets done just in time to save the day! Well, that's awfully convenient. Sci-fi does exactly the same thing with technology, obviously. It's broken, we need a widget, just a few more minutes---aaaaah! ...