Book of Acts – Audio Bible Reading / New Testament
The author of the Acts of the Apostles is the same author of the Gospel of Luke. Both books are addressed to Theophilus, and the latter (Acts) refers to the former (Luke). Luke the Physician was the author of Luke-Acts.
Luke is often neglected as a theologian. This is unfortunate because he has a very developed theology and also wrote a larger portion of the New Testament than any other author.
The main theological emphasis of the book of Acts is the Holy Spirit. The book begins with Jesus’ promise of the Holy Spirit, which is later fulfilled in reference to the Jews (ch. 2), and then for the Gentiles (ch. 10).  Reference to the Holy Spirit comes in a variety of ways. Many of the occurrences are references to a person being filled with the (Holy) Spirit: 2:4; 4:8, 31; 9:17; 13:9, and 52. Luke also equates the Holy Spirit with God (cf. 5:3 with 5:4),  and the Holy Spirit directly intervened in Paul’s life (16:6-7).
Luke also makes it clear that Christianity was not a threat to the Roman Empire through “the demonstration that Christian preaching does not impinge upon the power of the empire.”  The Jews accused the Christians of “defying Caesar’s decrees” and “saying that there is another king, one called Jesus” (17:7). Prior to the ascension, Jesus’ disciples asked him if he was going to restore the kingdom to Israel (1:6). He told them that it was not for them to know the times or dates that were in the Father’s authority, but told them that they would receive power from the Holy Spirit to be his witness to the whole world (1:7, 8). It is evident that Jesus was not sending out his disciples to bring in a new “earthly” kingdom, but to bear his witness to the present kingdom.
In proving that Christianity was not a threat to the Roman Empire, Luke also succeeds in showing that Jesus was a world messiah and not just another prophet. The message of Jesus was not limited to Israel but extended to the Gentiles as well. Acts concludes with an “open-ended mission to Jews and Gentiles” which is a reminder of an “unfinished task and the urgency of being identified with the ongoing advance of the gospel of salvation.” 
Paul’s ministry as an apostle is validated in Acts by a comparison with the apostle Peter. They both heal a lame man (3:1-10 and 14:8-10), and heal others-Peter heals the sick with his shadow (5:15, 16) and Paul heals the sick with his handkerchiefs and aprons (19:12). Both were recipients of jealousy from the Jews (5:17, 13:45), confront sorcerers (8:9-24, 13:6-11), raise people from the dead (9:36-41, 20:9-12), and were imprisoned and miraculously delivered from jail (12:3-19, 16:25-34).
Luke’s audience is clear in both of his volumes. He wrote to Theophilus (Luke 1:3; Acts 1:1). Unfortunately, there is not much known about who Theophilus was. Some of the possibilities are that he was Luke’s patron, or that the name Theophilus (which means “lover of God”) is being used universally as a reference to all Christians. Luke’s usage of the term “most excellent” (kratistoV) helps to identify this character. The word is a “strongly affirmative honorary form of address”  and every occurrence of it in the New Testament refers to governing officials (Acts 23:26; 24:3; 26:25).
The purpose of Luke-Acts may be ecclesiastical or apologetic. For ecclesiastical purpose, it may have been written in order to edify the church, serving as a history of both Jesus and his apostles. Or apologetically it may have been composed to make the case that Christianity was not a threat to the Roman Empire-more specifically, it seems that it could have been Paul’s defense before Caesar.  This last argument seems to fit the abrupt ending the best and is also supported through the acceptance (or non-conviction) of Paul from governing officials (18:12-17; 23:23-30; 26:31-32; et al.).