Cautions for Mere Christianity

I still think Mere Christianity is a great book, espically for non-believers (and they after all don't care much about different atonement theories): Cautions for Mere Christianity – Kevin DeYoung:

Pay careful attention to what Lewis says in that paragraph. He does believe in a substitutionary theory of the atonement, but he rejects penal substitution. He admits that penal substitution is not quite as silly as it once sounded, but he still does not accept it. Instead, he argues that Christ pays a debt (which is true), but not as a punishment for our sakes.