Circle of Three

Circle of Three is a young adult series by Isobel Bird about three teenage girls--Kate, Annie, and Cooper--who come together after Kate finds a book of spells in the school library and casts a love spell that has disastrous results.

Fantastical-sounding description aside, the series is actually about the girls' lives as they study Wicca, and presents it all (mostly) realistically.

There are 15 books in the series:
 * So Mote It Be
 * Merry Meet
 * Second Sight
 * What the Cards Said
 * In the Dreaming
 * Ring of Light
 * Blue Moon
 * The Five Paths
 * Through the Veil
 * Making the Saint
 * The House of Winter
 * Written in the Stars
 * And It Harm None
 * The Challenge Box
 * Initiation

This series contains examples of:

 * Alpha Bitch: Sherrie.
 * Author Tract: The series was written deliberately to show teens how Wicca is actually practiced in real life.
 * Character Development: The whole point of the series, particularly for Kate.
 * Deadpan Snarker
 * Girl Posse: The Graces
 * Magic Misfire: Starts the whole thing off.
 * Magic Realism: Certain aspects of the series, especially the bits dealing with ghosts and spirits, press the belief of even the most devout Wiccan.
 * Magick
 * Moustache De Plume: Inverted-- author Isobel Bird is actually Michael Thomas Ford.
 * Neo-Paganism
 * Power Trio: Duh.
 * Reincarnation: It is strongly implied that Cooper was in a Nazi concentration camp in a past life.
 * Tarot Motifs: All over the place, but mostly in What The Cards Said
 * You Fail Religious Studies Forever: Many, many in-universe examples, but mostly in The Five Paths