Just finished this-it's a fun read!
The Inheritance Games by Jennifer Lynn Barnes
Avery Grambs has a plan for a better future: survive high school, win a scholarship, and get out. But her fortunes change in an instant when billionaire Tobias Hawthorne dies and leaves Avery virtually his entire fortune. The catch? Avery has no idea why--or even who Tobias Hawthorne is. To receive her inheritance, Avery must move into sprawling, secret passage-filled Hawthorne House, where every room bears the old man's touch--and his love of puzzles, riddles, and codes.