Encyclicals are letters or documents released by popes during their pontificate. They are often not only educate the people of God, but encyclicals help one to grow in their faith through understanding.
Lumen Fidei Pope Francis (2013)- The latest encyclical on Faith.
Rerum Novarum Pope Leo XIII (1891)- Rights and duties of Capital and Labor. Discusses the condition of the working class. (A good read for a business owner.)
Ad diem Illum Pope Pius X (1904)- On the Immaculate conception.
Casti Connubii Pope Pius XI (1930)- On Christian marriage
Redemptoris Mater Blessed Pope John Paul II (1987)- His holiness discusses Mary, the Mother of God.
Deus Caritas Est Pope Benedict XVI (2005)- explaining Christian love.
Spe Salvi Pope Benedict XVI (2007)- Explaining Christian hope.
Caritas in Veritate Pope Benedict XVI (2009)- explaining charity in truth.