"... the Gospels did little more than to anticipate the church, whereas the Epistles presuppose it. A work was needed to describe the rise and development of this great spiritual entity that would at the same time be a binding element between Gospels and Epistles. The Book of Acts fills exactly that need."
January 1, 1970
https://en.wikiquote.org/wiki/Acts_of_the_Apostles