Midnight Echo,

Forget Sheppard Air, the FAA has changed the ATP written format. I used Sheppard Air for my written years ago and it was fantastic however, my buddy fell flat on his face on the written due to the FAA changing the questions.
If you plan on attending a job fair, it would be in your best interest to be interview ready. You'll need the written complete before you attend ground school, I'm not sure if you need it for an interview.
Read and heed what other posters have said. SKW training is very thorough and very fast paced. You cannot fall behind otherwise you're gonna find yourself in a world of hurt. With that said, the training department will give you all the tools needed to be successful. It's up to you to utilize the materials given to you. Hope to see you on the line, good luck.