The Book of Acts is a transition book. From Kingdom a believers to a Body of Believers. From Law to Grace. From the 12 Apostles dealing with Israel to one Apostle dealing with the one new man, where there is no difference between Jew and Gentile. No one “Laid down his pen”, and the story does not just “abruptly end”. The dispensation of the law was set aside and the dispensation of the grace of God was taken up. Acts is about the fall and temporary blindness of Israel. And the times of the Gentiles. Just like Hebrews is a transition Book, where God is once again dealing with Israel as a nation and the middle wall of partition that separated Jews and Gentiles is back up.It was noted by a Theology professor I studied under that actually Acts is actually the first NT book..the gospels all reflect the the OT law,which Christ fulfilled and that was eliminated at the cross when the new covenant was made ...
Thats why so many get confused, and think that law keeping is a means of salvation today ..
That is also what I believe. According to Hebrews 9:16,17 there is no testament without the death of the testator. Which means that Mathew, Mark, Luke and John are all part of the OT. For the most part. Until His death.