What a great find, I remember loving the movie when I was a young girl. This was a wonderful way to tell the story of Jesus, after the crucifiction and through the eyes of the people he had lived with and taught and healed, and a good reminder of what the Christian religion is truly about.
Marcellus and Demetrius were wonderful heros, I adored Diana, hated the evil Roman Emporers and thoroughly enjoyed immersing myself into the life and times of that era. I noticed some other reviewers claimed there were historical inaccuracies in the book which distracted them from enjoying it as much as I did. Not knowing enough about the various rulers of those times I can't comment on that, except that since the book was written in 1945 perhaps the known history was different than what is available now.
The book is quickest in pace at the beginning and the end, with a large slower period in the middle while Marcellus travels through Israel learning about the life of Jesus. However, I enjoyed the slower pace and reminder of the many wonderful things that happened at this time.
All in all a great read and highly recommended, with the caveat that if you are an agnostic or of non-christian faiths you might not appreciate it as well. Also a good choice for a younger teen reader, as you won't find the abundant gratuitous sex that you find in more current novels.