It's good and honestly better stories than the main game. If you had to pick 2, do Secret Armory and Zombie Island.
Since we're less than a month until 2 releases, it's your call. You'll be able to get through it before then, but if you're only going to play through them once, it might not be worth it. What's your level now?
This post was edited on 8/21 at 10:20 am