The Bible is the most famous book in the world, read by a countless number of Christians and others over the centuries. Even those who aren't Christian or remotely religious can rattle off Matthew, Mark, Luke, and John as the first four gospels of the New Testament, and books like Genesis and Exodus include some of the most famous stories in human history.
Of course, the Bible is composed of dozens of different texts that collectively combined to form it. The process of establishing which texts were canonical and included in the Bible took centuries of fierce debate among early Christians. Even today, not every branch of the Christian church agrees on which writings should be regarded as "canonical" and which are "apocryphal", even though some apocryphal texts often have noticeable links with books regarded as "canonical". It was only in the late fourth century AD that a proposed list of texts for the Bible was even put forward.
The New Testament Apocrypha refers to texts written by early Christians that were not included in the Bible used by the main branches of Christianity today. These texts vary in subject matter, with some being accounts of Jesus, others being about the nature of God, and still others being accounts and teachings of Jesus' apostles. What makes them fascinating is not just the history behind why they are considered non-canonical, but what they tell us about the early Church and early Christianity. Moreover, they offer insight into what sources were used to write them, and whether they shared the same sources as the texts that comprise the Bible today. Given their historical and religious importance, there is still a fierce debate over the authenticity of many of these texts.