IKE the Gospel of Luke, this book is addressed to a Christian named Theophilus (Luke 1:3 & Acts 1:1). Its content and format is naturally a continuation of the former book. In fact, it very naturally picks up right where the gospels left off. Jesus has completed His passion (Acts 1:3) and simply commissions and commands His disciples concerning that which was to come next for them. From the beginning of His ministry, Jesus was expected to baptize with the Holy Ghost. This discourse of Luke gives us an account of that event, and the effects of that spiritual baptism (Acts 1:5 & 8).
This is a book about evangelism. The propagation of the gospel of Jesus Christ (first in Jerusalem, and then spreading it out from there to the whole world) – this was the business of the apostles. Even today we are continuing that which was commenced during the days of the apostles. We are simply doing the work of the Messiah in His absence, as we wait for Him to return (Acts 1:11).
There was only a ten-day wait between the ascension of Christ and the entrance of the indwelling Holy Spirit into the church of Christ. However, it must have felt like a long time to the apostles. Each day they waited for something that they had never seen before. In faith, they almost blindly anticipated this blessing. What would it be like? What would the results be? When would this occur and how would Jerusalem respond to this invasion of God? The church was in its shell ready to hatch out into a brand-new world.