Other mistake: Shortly after the start of the movie, when Eric Bana's character reappears in the library and starts to put his clothes back on, his pants are already undone. If he had suddenly vanished from the library, then his pants should not be undone (unless, of course, he was up to no good just as he vanished).
Continuity mistake: When Henry goes to see Clare at the meadow and Clare is about 18 (after he gets the vasectomy) he kisses Clare, and each time they switch between Henry and Clare, the hair clips on Clare are a different color. The first are aqua blue and then they are yellow and back and forth for the duration of the scene.
Question: There's a scene in which, right after they've bought their house, Henry appears in their living room, naked and shot. I just don't see how this can happen because this would constitute a travel within a travel. That is, he travels to where he gets shot. Shot, he then travels to the newly-bought house; then finally travels back to the Christmas party from whence he came originally, where he finally dies. But the movie never establishes this sort of "Inception"-like travel. He always travels to one time, then comes back. Is this something that the book clarifies, or is it a mistake from the movie?