After filming was done, Eric Bana started filming Star Trek (2009), a role which required him to shave his head. However, re-shoots for this movie were needed, so production was put on hold, so Eric's hair could grow out. It took so long, that the movie's release date was pushed back by nearly a year.
The trivia item below may give away important plot points.
During the final meadow scene, after Henry disappears, Alba bends down to pick up his discarded brown loafers. This is a reference to the cover art of one edition of the book, which features a young girl (visible only from mid-leg down) standing next to a brown pair of loafers in a field.