How to Dig a Hole to the Other Side of the World by Faith McNulty. 1970.

Second person, a how-to booklet on digging to the center of the earth and beyond. Fact meets fun. The fantasy element combined with scientific detail make this a favorite and true classic. But hey, my copy didn't come with a CD!

That aside, my kids frequently dig holes around the yard, and they truly are trying to break through to the earth's core. So far we've gotten not much beyond two feet. But hey, when you're only four feet high, that's not bad!