I finally had the opportunity to sit and read it today and I gobbled it up in one afternoon. I super-enjoyed it! I loved all the twists and turns and it kept me sucked into it the entire way. I thought I had the bad guy figured out, then was thrown for a loop and loved how it ended. Going in, I didn't realize how supernatural it was, but it wasn't told in an alternate world; it was right here in ours, just with some "sparked" people. The rules of their existence were clear and necessarily mysterious too, but all reasonably believable. The characters were well developed, even the lesser ones, and the story itself (which I what I always grasp onto) is a really fun ride.
Maybe not important, but "Sparked" has similarities to "How to Hang a Witch" by Adriana Mather. This story has nothing to do with witches, but if you enjoy this one, you will probably enjoy the other, and vice versa.
One odd thing: it shows I listened to Audible, but I read it on my Kindle.