In the book, Betty Mahmoody and Mahtob escaped Iran thru the northern mountain regions in the dead of winter with severe ice and snow. The producers planned to film the escape scene in the Eilat Mountain in Southern Israel. However, there was no snow that winter and the escape scene was going to scrapped. Many protests arose because they felt the scene was essential. Sally Field even threatened to quit the project. The producers looked for other locations but either they were too expensive or unsafe for the actors and the crew. Finally, the scene was re written to have Betty Mahmoodey and Mahtob traveling thru the desert in searing heat.
The trivia item below may give away important plot points.
The book doesn't end as is shown in the movie. Mahtob and Betty arrive in Ankara, Turkey's capital where a hotel refuses to give them a room because their passports don't have entry stamps on them. Then they go through a bureucratic hassle with the help of the American Embassy and only after that they finally have safe passage to the States.