The Book of Ephesians is the epistle that addresses God's wonderful providence revealed through His Church in the New Testament.
Through the whole epistle, Paul leads us into the providence of God.. In other words, Paul makes it clear that God the Father had planned the salvation of mankind in Jesus Christ, fulfilled it through Jesus Christ and is now revealing this work of salvation that was accomplished in love through His Church.
The purpose of this book was to explain God's dispensation of salvation. Unlike his other epistles, it does not mention Paul's fellow workers. Through the whole book, the Apostle Paul wrote about how God the Father planned our salvation in Jesus before the foundation of the world and how He had accomplished the plan through the Gospel [the Good News].