My favorite books of the Bible (I can't choose just one!) would be Genesis, the four Gospels, and Revelation.
Genesis because: It tells Who created the world and how we got here. And also because it has some of the really familiar Bible stories in it. Like Adam and Eve, Noah's ark, Joseph's coat of many colors, etc.
The Four Gospels because: of Jesus! The four Gospels tell the life of Jesus and also they tell us how and why we can be saved!
Revelation because: it gives us hope that this world will not remain this way forever. And because it tells us what heaven is like!
What are your favorite books of the Bible and why? (I know I have a poll on the sidebar asking this question, but the space is limited and so I can't list many of the books. )