The Mortal Instruments: City of Bones; City of Ashes; City of Glass

In City of Bones, fifteen-year-old Clary Fray is introduced to the world of the Shadowhunters, a secret cadre of warriors dedicated to driving demons out of our world. And she's introduced with a vengeance, when Clary's mother disappears and Clary herself is almost killed by a grotesque monster sent by the evil and powerful Shadowhunter, Valentine. How could a mere human survive such an attack.
In the second novel, City of Ashes, Clary just wants her life to go back to normal--but that turns out to be impossible. For one thing, her mother is still in the hospital, in a mysterious coma. For another, she and her newfound brother Jace have fallen under a cloud of suspicion now that the Shadowhunter world knows that Valentine is still alive--and that Jace and Clary are his son and daughter. Then Clary's best friend Simon is turned into a vampire and kidnapped by Valentine, who intends to sacrifice him as part of a bloody ritual that will make the Mortal Instruments Valentine's forever.
In book three, City of Glass, Clary has to use all her ingenuity and newfound magical skills to get herself to the Glass City in Idris, the secretive Shadowhunters' home country, where she is forbidden to go--for it is only there that she can find the cure to the enchanted sleeping sickness to which her mother has succumbed. When Valentine attacks the city and destroys the demon towers, Clary and her allies are all that stand between him and the total annihilation of all Shadowhunters. Love is a mortal sin and the past tangles inextricably with the present as Clary and Jace face down their father in the final installment of the Mortal Instruments series.