Around chapter 12 shit goes entirely off the rails. Until then just about everything in the book made it to the movie in some form, but then Forrest Gump goes to space! The writing devolves into looney tunes caricature. They send him into space with a monkey that likes bananas and a woman, but they crash land in Borneo and get captured by cannibals who make them pick cotton, the female astronaut gets married to a tribesman named Guruck, and the chief (who talks with a New England accent because he went to Yale) teaches Forrest to play chess and finally tries to eat him after he finally manages to get him in check.

It's been a while since I watched the movie, and I might be getting things mixed up with Apollo 13, but I don't think Tom Hanks was ever about to be boiled alive in a giant cauldron by a tribe of bone-lipped stereotypes.