- John Carter was not running from the law. He was prospecting for gold with a partner when the indians attacked.

- The Holy Therns and their teleporting devices were not in the first book. John heard strange noises in the cave, then he found himself naked and looking down at his paralyzed body. He goes outside and looks at the sky. Mars is clearly visible and he finds himself pulled toward it.

- The entire story is told in first person from John's perspective, so the stuff with Dejah Thoris and her father in Helium and discovering how to harness the ninth ray energy was not in the book.

- The Tharks were far more brutal in the book. They were the ones who shot down Dejah's airship, not the Zodangans. John didn't rush in to save her, either -- he just observed the confrontation from afar as the Tharks took her prisoner and scavaged the ship for supplies.

- There are several other differences -- mainly the arena fight. John was pitted against other warriors in a last man standing death match. One of these men was an ally of the princess. He convinced John to pretend he had killed him so they could escape together and find her. There was something similar to this in the film, where James Purefoy's character tells John to take him prisoner. I suppose the circumstances are different in the film because they wanted a big spectacle with giant creatures. There was a white ape attack in the book, but it happened in the Thark city very early in the story

- Tal Hajus (the evil Thark voiced by Thomas Hayden Church) was behind the death of Sola's mother and Tars Tarkas's love. It was a big deal in the book that Tars wanted revenge on this guy, but in the film John just cuts off his head. The concept of love and family was considered a weakness to the Tharks. All the eggs were taken to an incubator and the children were raised by random caregivers. Tars was the first Thark to hide an egg from the community because he wanted to protect his actual daughter. I'm not sure how much of this came across in the film, but it was decent drama that I think would have worked well had they presented it better.

- IIRC, Dejah was not forced to marry anyone, but chose to do it for the good of her planet after she thought John was dead. When he returns, she still refuses him. Apparently a promise of marriage can only be broken by death on Barsoom. As I recall, the Zodangan prince was not an outright villain in the book. Nevertheless, he had to be dispatched so our hero could get the girl.

- There was an entire climax where John attempts to restore power to the planet's oxygen factory that was removed.

- And perhaps the biggest change/loss: Dejah was pretty much naked throughout the entire book.