One of my favourite depictions of magic in fiction is Bernard Cornwell's books about Arthur. Merlin's there and so is Nimue & there is a lot of magic, but the magic is fickle and difficult to predict and control, and even when it SEEMS to work, the reader is left to wonder what actually took place.
In the story, the characters using magic knows it's dependent on the old gods, and those gods are not always cooperative. There is no sure way to make something happen with magic, but intent and confidence seem to matter, even though Merlin more than implies that a lot of it is also showmanship.
Mine is in the Earthsea books by Ursula K. LeGuin. I like it because magic isn’t free. It’s important, a part of nature, must be used sparingly so the world stays in balance. There are consequences to misuse & overuse. It’s not like Harry Potter where magic is used frequently for trivial reasons.