The Mortal Instruments series by Cassandra Clare is a fantastic young adult fantasy series that follows the adventures of Clary Fray, a teenage girl who discovers she is a Shadowhunter, or a human with angelic blood who is tasked with hunting down demons.
The series consists of six books, and it's one of the most popular YA series out there. The books are well-written and action-packed, and they're sure to keep you entertained from start to finish.
If you're looking for a great book series to get into, I highly recommend The Mortal Instruments. You won't be disappointed!