This is the thirteenth novel in Pratchett’s Discworld series. It is the story of a slightly stupid monk named Brutha. Brutha’s job and greatest joy is working in the monastery’s vegetable garden, a place where food grows in the ground as slowly as a thought grows in his mind. However, fate had much bigger plans for Brutha than growing lettuce.
When the tortoise first started speaking to Brutha, he assumed he was going crazy. When the tortoise started telling him that it was actually the Great God Om, Brutha assumed he was being tempted by a demon. When his faith was strong enough for him to accept that the tortoise actually was the Great God Om, Brutha began the transformation from simple minded gardener and novice monk to the greatest prophet his faith has ever known.
Shortly after Brutha began carrying around a tortoise and speaking to it he was chosen by the head of the Omnian question, Vorbis, to accompany him to the neighboring town of Ephebe. He was chosen because even though he had never learned how to read and really hated to think, he was gifted with an eidetic memory that Vorbis thought would come in handy. They were going to Ephebe because there was a group of people there who were worshiping the Great Tortoise, because they believed the world was a flat disc riding on the backs of four giant elephants, which were in turn riding on the back of an even more giant tortoise. This seemed insulting to the Omnians, because they believed the Great God Om was the only real God, and that he would never manifest as something as lowly as a tortoise.
While in Ephebe, Brutha and Om became acquainted with three philosophers, and while talking to them Om came to the disturbing realization that even though many people worshipped him out of habit or due to fear of the Quisition, Brutha is the only person left who truly believes in him. This was a problem for Om because a god’s manifestations and powers are dependent on the number of believers they have, and if anything were to happen to Brutha, he would fade away. Fighting broke out between the Omnians and Ephebians, and Brutha memorized many scrolls from Ephebe’s extensive library before escaping in a boat. Brutha and Om wound up trekking back home through the desert with a badly injured Vorbis, and Om spent many anxious hours protecting Brutha from the various small gods floating through the desert looking for someone to believe in them. Once they came to the edge of the desert a recovered Vorbis tried to kill the tortoise, abducted Brutha, and rushed to Omnia to be declared the eighth Prophet.
Back in Omnia, Vorbis ordered Brutha to be publicly burned for heresy on the back of a brand new torture device that looks like a giant turtle. At the last possible moment, Om fell from the sky onto Vorbis’s head, killing him instantly. Upon seeing this miracle, many people began to once again truly believe in Om and he became powerful once again. He then named Brutha the eighth Prophet and allowed him to establish the new Church doctrines. Together they avoided war between Omnia and Ephebe, and Brutha lived on for another one hundred years, turning what was supposed to be the bloodiest century in Omnian history into a century of peace.
I guess what you get out of this novel depends on how you choose to look at it. Some people think it’s purely a fun read, some people think it’s a commentary on today’s religious disagreements, and some people think that whatever it was meant to be, it was horrible. I enjoyed it, but I wouldn’t use it as a way to frame my opinions of real world religious dynamics. Another good thing about it is that even though it is a part of the Discworld series, you don’t have to know any of the Discworld culture or backstory to enjoy it, so if you are wanting to familiarize yourself with Pratchett’s books it’s a good one to try.