The Readings from Scripture are three. Normally, one reading is from the Old Testament, another from an Epistle of the Apostles, and then a reading from one of the four Gospels.
A Lectionary is a book that orders the Scripture readings for the entire year. There are two lectionaries in the LCMS: 1 year and 3 year. The 1 year lectionary is the Historic Lectionary of the Christian Church. It has its beginnings in the early church and developed through time. The 3 year lectionary was created by the Roman Catholic Church in 1969. Protestant churches and Lutherans would adopt and modify this lectionary.
Today, you can find a Bible anywhere. Ranging from cheap to expensive. But for thousands of years, the reading of Scripture in synagogue or church was the only way for the ordinary man and woman to hear Scripture. Before the invention of the printing press, you had to be well off to pay a scribe to make you a hand copy of the Bible.