One of the most interesting reading experiences I have ever had was my library's copy of this book, in which a previous reader had added extensive commentary in the margins from a Muslim perspective. It was a fascinating mixture of agreement and disagreement that I can only sum up as "Yes, Christianity is wrong, but for this completely different reason."
My grandfather, who I never met due to certain family rifts, converted to Islam as an adult and wrote a book called "Answers from an Atheist" or similar, I forget the exact title now. In it he documents a discussion between an imam and an atheist. I found it fascinating reading when I was a young teenager, but started to find the discussion from both sides ridiculous after a while. By the time I finished it, I was pretty well convinced that he'd made the whole thing up as a way to have an atheist pitch softballs at an imam so he could give easy answers without having to actually defend his beliefs. But it started me down a years long reading adventure of different religious views and arguments, including Russell's essay mentioned here.
Idle curiosity: did reading that give you any kind of "connection" to your grandfather? I've been on a genealogy kick lately and I like when I can find artifacts from relatives I never knew, but I'm curious whether something that's argumentative and not quite as personal would have that same feeling.