"The book of Acts is the story of early Christianity."
Actually this book does not contain the acts of the apostles as a whole. The fact of the matter is, very few of the apostles are even mentioned in it. The book is largely limited to the ministry of two of them—Peter, who was one of the twelve, and Paul, who was an apostle of a different order altogether and not one of the twelve. He did not know our Lord on earth, but received his commission directly from Heaven. Actually the book might be called, as others have suggested, The Acts of the Holy Spirit; or, if you will, The Acts of the Risen Christ through the Holy Spirit Working in the Church on Earth. In this book we have brought before us in a wonderful way the work of that promised Comforter who came to earth to witness to the glory of our Lord Jesus Christ and to convince men of sin, and of righteousness, and of judgment.