The writer of the Gospel of Luke and Acts is generally known as Luke (although the author doesn’t write this himself, the name of the Gospel is not part of his text but was added later). From the early church on this book was known to be written by this person, called Luke, who accompanied Paul on some of his journeys (hence the ‘we’ parts in Acts, for example Acts 16:11). Paul writes about him in his letter to the Colossians (4:14). We also learn here that Luke was a physician.
The unfolding plan of God
One of the things which Luke is very interested in is to portray the Gospel as the unfolding of God’s plan. For example, Luke writes down how Jesus says to his disciples after his resurrection: “Thus it is written, that the Christ should suffer and on the third day rise from the dead, and that repentance and forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem….” (Luke 24:46,47). Luke emphasizes the history and the plan of God. We read at the beginning of his gospel how Luke “followed all things closely for some time past” and wrote his Gospel with the intention to show Theophilus “the things that have been accomplished among us” (Luke 1:1-4). Thus we see the picture of the history of the world where the mighty emperor Caesar Augustus decrees that all the world should be registered, the way in which Christ is born in Bethlehem (Luke 2:1-7), while the book of Acts ends with the fact that the apostle Paul is in Rome, the capital city of the Roman Empire, “proclaiming the kingdom of God and teaching about the Lord Jesus Christ with all boldness and without hindrance” (Acts 28:31). So who is the real king in the end?
Work of the Holy Spirit
Next to the history of God’s salvation, Luke is also the Gospel writer who writes a lot about the work of the Holy Spirit. In Luke 1 and 2 we see how the Holy Spirit leads people so that they do the will of God. John the Baptist will be filled with the Holy Spirit (Luke 1:15), the Holy Spirit comes upon Mary so that she conceives (Luke 1:35), Elizabeth is filled with the Holy Spirit and encourages Mary (Luke 1:41). Zechariah is filled with the Spirit (1:67), the Spirit is upon Simon and has given him a promise and guides him to the temple (2:25-27). John the Baptist promises that the one who will come after him will baptize with the Holy Spirit and fire (3:16) and this we see happen throughout the book of Acts (starting with the day of Pentecost (Acts 2)).
The compassion of Jesus
Luke shows the compassion Jesus has for the marginalized: the poor, women and non-Jews. To give but one example of each: Luke writes the parable of the rich man and Lazarus (Luke 16:19-31), in which the poor Lazarus goes to heaven while the rich man goes to hell. Luke is the one who tells us about the women who followed Jesus (Luke 8:1-3). Luke is also the one who tells us of the parable of the good Samaritan (Luke 10:25-37) in which Jesus takes a Samaritan (one of the worst enemies of the Jews in Jesus’ days) as an example of what it means to love your neighbor..
How God is in charge
In short, through Luke God teaches us how He is in charge of world history. Besides the reconciliation through Jesus’ death, Jesus also won for us the Holy Spirit who teaches us to witness to Him and follow Him. In Jesus’ Kingdom, God looks for the marginalized and brings them together in his kingdom. The kingdom is theirs (Luke 6:20-23) while at the same time this message warns people who think they are rich and important to be rich in God instead (Luke 12:13-21).
Read more in What is the Bible?