What's the proper etiquette when gifted with (hilarious) prosthelytizing religious gifts from love ones?

So just checked the mail and got a package from “Christian Television Network Homekeepers”. Naturally I laughed, clearly they don’t know who they’re addressing. Flipped it over “gifted by [my grandma]”. Ouch.

Inside:
one self-published creationist mega-pamphlet
and an apologetic letter reading:

Dear HOMEKEEPER Friend,
I want to apologize for the fact that you are receiving this order much later than we planned to send it. The demand for this book has been so great, Dr. McMurtry [not a real doctor] had to have more of them printed, which took longer than expected.

Thanks so much for supporting this ministry.

[End of letter]

Naturally I will read this book and make much fun of it on the internet. What I don’t know about is what to say about it to the nutty, Catholic, Eastern European grandmother who I never outed myself as a atheist to for obvious reasons. I’ve been getting hints from the family that she either knows or suspects and would like to handle this in a manner fitting Emily Post.

It should be known this is not a woman with whom I can have a meaningful discussion about religion or my lack of it. After Christmas I faced the novel problem of whether or not to wish her a happy new year in my thank you note having received her “Merry Christmas the world is ending” newsletter that December.