Of course the book was more thorough, and it better illustrated the tedium of Ender's struggles. There was also a pretty significant sub-plot in the book centered around Peter and Valentine (Ender's siblings) which was thoroughly ignored by the movie. However, the movie did employ some impressive eye candy, and it didn't deviate too much from the 20% or so of the book it summarized. If you enjoyed the movie, I think you'd doubly enjoy the book. But not the rest of the series. The first book is the only one in the series worth reading.