I just finished reading this series. There are few novels that I feel compelled to pick up outside of my subway commute, and these books belong to that category. I did not unequivocally love them, but they were all good reads. Think Harry Potter but young American adults who curse and have sex; or a dark The Lion, the Witch, and the Wardrobe.
While reading the first two books, I really wanted magic to be real. When I was in my late twenties or early thirties I tried some candle magick, and nothing came of it. It's possible that I just was not able to summon strong enough emotional energy and will it into a change in circumstances. But then we get into tricky territory, like "Be the change you want to happen" or all that The Secret philosophy. Of course that's different than shooting light out of your fingers or flying, but essentially I think magic is about our emotions and our surroundings being One.
One takeaway from these books is that you have to know yourself and know what you want to create something new. There is no room for ambivalence in magic, or at least if you're ambivalent the results of magic could turn out grotesque or half-formed. As a Pisces -- which is a mutable sign -- I often swim in both directions at once, so don't have the strong I have to go in THIS direction and abandon everything else that I associate with a zodiac sign more suited for magic, like Scorpio. So maybe if magic is real, it's just not for me. I tend to be more suited towards changing consciousness than changing matter.