The only difference between the endings of the book and the film is that in the book it takes a few days before the boy encounters the family near his father's body rather than right away. Otherwise it was a pretty faithful adaptation.
Starship Troopers, on the other hand, was an absolute travesty of a film. I think I've said this before but Paul Verhoeven makes a bad movie, someone says "this is a bad movie" and then Paul Verhoeven says "ah, no, it's satire."