what exactly was the need to change the plot so much?..

I just read the synopsis of the book Z for Zachariah (mainly because I couldn't understand after watching the movie how the title made any sense), and it sounded a lot more interesting. At the very least it sounded way more realistic than a young girl actually being willing to build a life with an unattractive older man.

What a waste this movie was... I don't know why it got such a high rating from the critics on Rotten Tomatoes, but I definitely should have paid more attention to the user one.