My DD is 3 in 2 weeks, she has always loved books and would be read to for hours if she could. We also mostly listen to stories in the car as that is what she prefers over songs. I think as a consequence of this she is pretty articulate, people are generally surprised with the vocab she comes out with. Just recently she has started narrating bits of her life, for example we were getting ready for bath the other day and she said "the girl got undressed. "Brr, she said as she shivered" - I swear this is exactly what she said. This happens throughout the day, she says something to me and then as a sort of aside makes some comment not to me in the way you have in a book.
I am in no way worried, but I have never seen this before in a child - I have always worked with nursery age children. Has anyone else ever had this?