Ian Caldwell mixes together the Shroud of Turin, a lost gospel and the rivalry between the Roman Catholic and Greek Orthodox churches in his well-written religious conspiracy thriller, The Fifth Gospel.

The book is set in 2004 and opens with Father Alex Andreou, a Greek Catholic priest working in the Vatican, being frantically summoned by his brother Simon, a Roman Catholic priest, to the Castel Gondolfo.  Once there he finds Simon soaking wet and standing over the murdered body of Ugo Nogara, the curator of an important forthcoming exhibition about the Shroud of Turin.  Later that night there is a violent break-in at Alex's apartment and Ugo's notes go missing.   The police begin to suspect Simon of the crimes and Alex's life is thrown into chaos.

In order to find the real killer and prove his brother's innocence, Alex must reconstruct the dead curator's secret and work out what the four Christian gospels, and a little known fifth gospel known as the Diatessaron, reveal about the Shroud of Turin.

The Fifth Gospel provides a wealth of fascinating information about the history of the Gospels and their meaning and the schism between the Catholic and Orthodox churches. There is also an abundance of detail about everyday life in the Vatican and the intricate nature of Catholic politics.  Caldwell has clearly done his research and much of the information is interesting, but he has the tendency to just dump it on the reader in indigestible lumps.

The main characters are refreshingly different from the usual thriller types, especially Alex, who is a simple man of the cloth trying to raise his five year old son in the confines of the Vatican.  Greek Catholic priests are allowed to marry, however Alex's wife abandoned him and their son in a fit of depression a few years before.  Alex loves his son, but is finding it increasingly difficult to raise him alone in the Vatican.

Alex and his brother are good people, but at times the reader is likely to wish that they were more decisive and action-oriented.  The pacing drags in spots and is not helped by Caldwell's alternating between revealing flashbacks and current time in order to keep the reader guessing.  This adds to the mystery, but becomes irritating and slows the story.

In all The Fifth Gospel is a fascinating and intriguing novel, but lacks the energy and excitement to make it a compelling thriller.

Jeff Popple is a Canberra reviewer.