Our son Malachi was reading his Bible some time ago and was getting its meaning clearly. Let me be sure to add that, at the time, he was a few months shy of two years old. Nevertheless, he really was understanding the Bible. I know I have skeptics out there readingthis saying, "hey bro, two year olds aren't theologians yet." Ahh, you must not have kids yet.
As he was flipping through his Bible (granted a mostly picture-Bible), he would look at a page and say "Jesus", then flip a page and say "Jesus", another page, "Jesus"...flip agin..."Jesus...Jesus..." all the way through the whole Bible with each page.
He gets it. He may not know words like "propitiation", "expiation", "paedobaptism", and "postlapsarian", but he gets "Jesus"...that all God's word is about Jesus.
"Out of the mouth of infants and nursing babies you have prepared praise" (ESV, Mt. 21:16 quoting Ps. 8:2)