Why is the book of Acts exciting to study after you see this transition?
The book of Acts becomes exciting once the transition is seen: Israel continues rejecting the Messiah and fades from the scene, while Gentiles enter God's favor under grace. The departure from Peter and Israel to the conversion of Saul and Cornelius makes the unfolding program so obvious that the narrative's direction is clear.
Les explains that the first part of Acts is nothing but Peter and the nation of Israel. Then suddenly there is a departure: the conversion of Saul, and in chapter 10 Peter goes to the house of a Gentile, Cornelius. Gentiles are something new. What is coming is Israel going off the scene, and Gentiles coming in to God's favor under the whole system of grace. Once you see that transition, Les says the book of Acts is so exciting to study because it becomes just so obvious what is happening. Peter is still sticking to the Old Testament prophets and the Old Covenant program, as shown in his appeal to Moses and all the prophets from Samuel onward who foretold these days. The transition makes the narrative clear.