One of the books that Liesel read to Max when he was sick is actually the book The Book Thief itself, containing the sentence: "what came to her then was the dustiness of the floor, the feeling that her clothes were more next to her than on her, and the sudden realisation that this would all be for nothing".
While in the basement, Hans comments that the snowman will not melt because "it's freezing down here," yet no character's breath can be seen in the air, despite the fact that all are breathing heavily.
When Liesel is seeing Hans off at the train depot when he's been conscripted, she is standing several cars down from the engine, facing toward the front of the train as Hans steps aboard one of the passenger cars and we can see at least one other such car between his and the engine. The camera angle then changes and we see Liesel has not moved but as the train begins to move forward, she is beside the coal car.
When Liesel is climbing in the window to steal books from the library, she knocks two books off the table. When she picks them up, the direction the books are facing changes between shots.