Three possible explanations have been offered.
1. Jack died from his head wound in Iraq, and everything that follows is a dream or hallucination that he experienced just before he died.
2. Jack survived the wound, suffered amnesia, moved back to Vermont, actually met Jackie and her mom, but everything else is a dream or hallucination that Jack experienced while confined by the jacket.
3. Jack's experiences were real and that he was actually able to transcend the drawer and move into the future.