This movie is based on the book by
Nikos Kazantzakis, who was
excommunicated from the
Greek Orthodox Church after writing it.
The Last Temptation of Christ was originally written in Greek, and there is apparently a great deal of connotation that is not easily translated. I have read that Kazantzakis used Greek neologisms and archaic words whose implications do not carry over into English.
Like all adaptations, it has to cut out a number of major plot points and simplify others. Despite that, it does remain basically faithful to the plot and theme of the book. Among the major highlights of the book that don't carry over into the movie: in the extended temptation, Mary Magdalene is killed and so Jesus ends up in a bigamous relationship with Mary and Martha, and Matthew (the apostle and evangelist) is directed by an angel to write down the historical untruths (such as the Nativity story) presented in his Gospel. If you have done some research into the early history of Christianity, the book is neat because it refers to most of the legends and stories about Jesus, both in and out of the Bible, and accounts for most of them.
A note about the movie: seeing it is what began my real entry into Christianity.