Gospels are a genre of ancient literature concerning the life of Jesus. The word derives from the old English word for Good News. The Greek word for Gospel is evangelos which means 'good news', since the retold the 'good news' of Jesus coming to the world. Each of the books reveals, by telling the story of Jesus Christ's life, the "Good News" about Christ's life and presence.
The Gospels are not biographies in the modern sense of the word, but rather celebratory expositions of a theological message that derives from Christ.
Many gospels were written in antiquity, but only four were eventually accepted by the mainstream Christianity of the period:
The first three books ( The Gospel of Mark, The Gospel of Matthew, and The Gospel of Luke ) are similar in style, even to the point of having several passages in common, so that they are collectively known as the synoptic Gospels (from the Greek, meaning "same eye"). See the synoptic problem. In order to explain the origins of the synoptic gospels, a hypothetical gospel "Q" is often theorised to have served as a source of these three works, and attempts have been made to reconstruct its text.
The fourth book, The Gospel of John, is quote different in tone, often full of more encompassing theological and philosophical messages.
The Diatessaron was an attempt to harmonize the four gospels into one. Eventually it fell into disuse, although it was popular for a while in Syria. But modern Gospel harmonies can be considered its descendants.
Marcion of Sinope believed in two different gods, the compassionate God of Jesus and the cruel God of the Jews. He developed his own edition of the Gospel of Luke, without texts he considered to forgeries placed there by the God of the Jews.
See also Secret Gospel of Mark.
Other books, which were not accepted, form part of the New Testament Apocrypha, and include:
Some of these works are similar in style and content to the cannonical Gospels. Others are works in which Jesus features as little more than a mouthpiece for Gnostic doctrine.
Other works claiming to be gospels have surfaced in later periods. The Gospel of Barnabas originates in the mediaeval period. Works from the modern period (sometimes called modern apocrypha) include the Aquarian Gospel of Jesus Christ and the Life of Issa. Parts of the Book of Mormon can also be considered to be a gospel, since they purport to tell of Jesus' appearances on the American continent.