The Book of Acts is written as a theological history of what Jesus is continuing to do and teach through the Holy Spirit in the Church to work out the kingdom of God in this world. Acts is concerned not just with geographical expansion but with the varied demands of cross-cultural communication of the gospel.
Acts is showing what it means (and doesn’t mean) to say that the crucified and risen Jesus is now installed as the world’s rightful Lord. It doesn’t mean a political and military takeover; in fact, Jesus’s followers routinely suffer persecution and death. It does mean that Jesus’s sovereignty is challenging the world’s rulers and authorities; not with force, but with a mixture of love and clear thinking and speaking.
Acts is also showing how a new power, the breath of God’s spirit, is unleashed through Jesus’s followers to transform human lives and communities; creating the Jesus-believers as a world-wide family across traditional boundaries and renewing individual lives.