I heard the movie was basically ready to go when someone noticed how similar the story was to Starship Troopers. They had to get the rights just to avoid a lawsuit. I'm not really sure I agree on how similar they are.

>The movie followed the book pretty closely except for the mecha-suits.

There's a surface similarity but the tone is completely different. To me, the film is pretty obviously a largely satirical retelling of the book's story.