Mere Christianity is trash. Couldn't even get through the first chapter because he calls out atheism almost immediately and basically says it's not even worth discussing because it's stupid and not an actual philosophy, which just strikes me as pure intellectual laziness, especially in a book about religion. Avoid, especially if you're an atheist trying to approach religion.
It's the very beginning of "Book Two" of Mere Christianity. Not only were his direct quotes about atheism just generally terrible, his logical argument about atheism was equally terrible. I'm genuinely surprised he's hailed as this great theologian or philosopher when he can't piece together a simple argument about theism vs. atheism. Like truly, these arguments in Book Two sound like some teenager in a youth group wrote them.