God is not too tired to work in this century. He is still in the world-changing business. And He is at work today, too. The Preaching of the Book of Acts. The main theme of the preaching of the apostles is the resurrection of Jesus Christ and demand for repentance on the basis of that message.
Acts is a book of Prayer.
The Christian life cannot run without prayer any more than a car can run without gasoline. These are not mere history books. They are not just recording early Christian history. If they were, then there are things that ought to have been added. Luke states that his primary purpose in writing his Gospel account was to give an account of the teachings of Jesus.