Apple USB SuperDrive

If WheelieNick's suggestion does not work for you there are a few more to try.

From If you can’t eject a disk on Mac, try these solutions

If you can’t eject a CD or DVD

1. On your Mac, choose Apple menu  > Log Out, then log in again. Try to eject the disc again.
2. If you still can’t eject the CD or DVD, choose Apple menu  > Restart. While your computer restarts, press and hold the mouse or trackpad button until the disc is ejected

Why It doesn't read I don't know, have you connected it to an enough powered USB Port?

You can eject the disk by going to finder, select the disk in the bar on the left en press the eject button