@Emmybell: Adele did not write this! And this is an awful cover!
The only half-decent cover is Ronan Keating's. Both Bob Dylan (who did write this song) and Ronan Keating manage to show the real emotion; Adele makes it depressing, you said yourself "sad song", it's not. At all. I find it tragic that people only learn about songs such as this when over-hyped pop stars make shitty covers.