The Hidden Code — P.J. Hoover

Eleven years ago, Hannah Hawkins' parents disappeared while traveling abroad. Presumed dead, Hannah and her uncle are shocked when a letter from her mom arrives right after Hannah's sixteenth birthday. By piecing together cryptic hints from the note and other clues left behind, Hannah realizes her parents disappeared while trying to find the mysterious Code of Enoch, an artifact they believed could hold the key to curing disease -- or creating it. Hannah's parents had been determined to destroy the Code, no matter the cost. Now with the help of her uncle, her best friend, and another cute but not entirely trustworthy guy, Hannah sets out to discover what happened to her parents and if the Code of Enoch is real.