L. K. Andersen 
The Children of Light [EPUB ebook] 

Kaytlin Jorgensen is an average teenage girl, or so she thinks. A strange man appears outside of her South Florida high school chemistry lab just before an explosion turns her life upside down. Kaytlin’s family is kidnapped by a ruthless rogue element of the government, and she is the ransom. Kaytlin, her group of friends, and a grandfather who has just come into her life, must outmaneuver her pursuers to find her family and free her captive grandmother.