The Blood Moon

Brother witches Josh and Chris have sacrificed a great deal for their magical responsibilities. Their Aunt Kathy is the only family they have left, and together they must face their enemies to keep them from targeting any more victims. But when Kathy is put in the hospital after an attack, the boys are a witch short.
With the brothers at their weakest, they uncover a growing new power trying to organize the demonic hierarchy. Josh and Chris are left alone to battle an evil stronger than anything they've ever faced. An evil so strong it might cost them their lives.
The Blood Moon is the third book in the Under the Moon series, which is a part of the Art of Magic universe, containing the Lost By Magic and the Coven series.