"It depends on how attached you get to books," insisted Rachel McAdams, who will star in the movie opposite Eric Bana when it hits theaters on Christmas Day. "Because, you know, the films always change [things]."

Published by Audrey Niffenegger in 2003, the book told the story of a man who suffers from a genetic disorder that has him time-traveling, usually at inopportune moments. His wife, an artist who tries her best to love him despite his unpredictable condition, finds her past and future intertwined as Henry (Bana in the film) experiences the entirety of her life experiences.

"This film really centers on the love story," McAdams said of the choices director Robert Schwentke ("Flightplan") has taken with the film. "The book does as well, but the film is really distilled down to the love story."

These days, the "Wedding Crashers" breakout is hard at work promoting "The Lucky Ones," a military film that has her portraying a wounded soldier on leave from the war. But as a longtime lover of the "Time Traveler's Wife" novel, McAdams wants to make sure that her fellow fans are prepared for some things being different in the film.

"You have to go see the film with a very open mind that it will be different from the book," she explained. "Because you're talking 400-some-odd plus pages, and squishing it down into 90 minutes."

But most importantly, the "Notebook" star promised that this one will not be a chick flick: "No," she laughed.

"It's an amazing book," McAdams grinned, saying every person has to make their own personal decision when to read it. "It's up to you."

Do you prefer to read a novel before you see the movie, or afterwards?