I guess I am pretty lucky. I became an atheist not too long ago, and I graduate from High School in 4 months. I don't have to tell them. I won't lie about it though, if they happen to find my Richard Dawkins and Sam Harris books (which I am not hiding).
Anyways, since this is a satirical spoof, it may not mean anything to them. Tell them that you are reading it to strengthen your faith, as many Christians would do. I used to a be a Christian, and I used to do the same thing.
If that doesn't work, you could always follow my other path, which includes doing the following things (in any particular order):
1) reminding them that your faith is your business
2) reminding them that faith cannot be forced or coerced
3) yelling "Fuck you!" many times (has worked for me, but only because of my... unique.... circumstances)
4) running away for extended periods of time, giving them a chance to remember why they loved you in the first place (easiest if you can drive and/or have a place to stay at. I usually just chill at one of my friends' house)
May the glorious Flying Spaghetti Monster bathe you in his wondrous Mercy, Love, and Garlic Sauce!
May He bless MP3 Fiesta
and their noodlicious music bargains!
May He also watch over Roffleopolis
and touch it with his marvelous Noodly Appendages.