I only know of two books that debunk christianity from an atheist perspective (there aren't any that are written from a Satanic or a Pagan one):
Nailed by David Fitzgerald
Proves that the Jesus character never existed historically and it's just made up. Available as a free PDF here
All That's Wrong with the Bible by Jonah David Conner
Shows all the errors, contradictions and absurdities in the buybull. Available as a free EPUB here. Convert it to PDF here.
try getting the bible and quran in pdf and show him/her their content.once he/she sees the violence,antiscience etc in there,there's no chance he/she won't understand and give up that so-called "faith" in that filth(unless,of course,the person you're talking with is either a total retard or a filthy degenerate;i don't think the "shill for jews to get riches and influence" option is the case)
I only know of two books that debunk christianity from an atheist perspective (there aren't any that are written from a Satanic or a Pagan one):
Nailed by David Fitzgerald
Proves that the Jesus character never existed historically and it's just made up. Available as a free PDF here
All That's Wrong with the Bible by Jonah David Conner
Shows all the errors, contradictions and absurdities in the buybull. Available as a free EPUB here. Convert it to PDF here.
If he's christian I doubt he will have the stones or drive to actually read a book exposing it. It doesn't get much better than exposingchristianity.com anyways.
Nonetheless, there is always "The Anti-Christ" by Friedrich Nietzsche and "Julian the Apostate - Against the Galilaeans: Roman Paganism’s Champion Argues against Christianity"
Not dangerous, but outsiders usually don't click links to random forums or websites they don't know about. This is a mistake many SS make. They believe because they like and click every link to JoS forums, every outsider will do the same thing. They don't. Believe me, I have tried this many times with links to JoS when I was new and I wanted to promote it. They got very few clicks.
It's better to just give him the titles of the books. Or just post pictures of memes exposing xianity.