First off, let me say that if you are looking for a true to life portrayal of the Wiccan faith, look elsewhere. Yes, the author has taken great pains to stay as close to the actual practice as possible, but she still takes several liberties in order to make for a good story. Even so, this is one of the very few mainstream series I've read that actually gets the main gist of the Pagan religion. 
 Now for the story. The story focuses around Morgan, a somewhat normal girl. When the cute new boy in school asks her to come to a field for a secret party, she jumps at the chance to do so. (As does her best friend.) Once there she discovers that the new boy Cal wants them all to help perform magic, and despite some initial misgivings Morgan does. What follows after is a discovery about her true potential as a witch as well as her taking the first step in a path that will eventually put everyone she loves in danger. 
 Like I said initially, there's a lot of liberty taken with the whole Wiccan religion. They bring in the idea of "Blood Witches" that come from a specific bloodline as well as add in magic that isn't possible. Don't take offense at this- maybe it's overly done but it's still more realistic than half of the other series out there right now & the author does do the research. 
 The best way to describe this series is to compare it to a piece of chocolate. It's way yummy & fun, and when each book is about 160 pages the books don't seem to last very long. It's very much worth reading & I recommend this series to anyone with a hunger for fantasy reading.