I recently posted on the thematic links that tie Luke and Acts together. Steve Walton has a couple of good paragraphs on this as well. Walton writes:
"Reading Luke and Acts together, on the other hand, can explain some puzzles. Such an approach is suggestive for Luke’s apparently diminished emphasis on the death of Jesus in Acts, for Luke has told this story clearly in his Gospel and, while writing Acts, can count it as read and known. The clear statement of Acts 20:28, seeing the blood of Jesus as ‘obtaining’ his people, is the tip of a large iceberg of understanding of Jesus’ crucifixion found in the Gospel, notably in Luke 23 (Wenham and Walton 235)."
Steve Walton, "Acts," in Theological Interpretation of the New Testament: A Book-by-Book Survey, ed. Kevin J. Vanhoozer (Grand Rapids: Baker, 2008), 79.