Cynthia Leitich Smith
Check out the book trailer for Timeless by Alexandra Monir (Delacorte, 2011). From the promotional copy:
When tragedy strikes Michele Windsor’s world, she is forced to uproot her life and move across the country to New York City, to live with the wealthy, aristocratic grandparents she’s never met.
In their old Fifth Avenue mansion filled with a century’s worth of family secrets, Michele discovers a diary that hurtles her back in time to the year 1910.
There, in the midst of the glamorous Gilded Age, Michele meets the young man with striking blue eyes who has haunted her dreams all her life – a man she always wished was real, but never imagined could actually exist. And she finds herself falling for him, into an otherworldly, time-crossed romance.
Michele is soon leading a double life, struggling to balance her contemporary high school world with her escapes into the past. But when she stumbles upon a terrible discovery, she is propelled on a race through history to save the boy she loves – a quest that will determine the fate of both of their lives.