What was first the chicken or the egg? Ender´s game book was written at 1985 and if you read it most of the things from film are at it.
Other point would be how at least for me the alien starships on the film do not look as the vasari. The bigger starship reminds me to one piece of tree eaten by ants, even by the colors. At the end, I return to the original book with my thoughts because it is very descriptive about how things look.