I didn't read/see Battlefield Earth, but, while I think the twist would have been transformed from cute to incredibly lame in a longer piece of fiction.
the book doesn't rely on the number system as a 'twist' it's actually an integral & logical plot device of the story.
and the book compared to the movie is not is very fare to the book. the book is actually a very entertaining, pure scifi read. and from what i do know is that the book isn't wholly written by l ron, the same that the mission earth series is ghost written by other folks.
if you ever have a 6 month med cruise on board an aircraft carrier you will find many varied books to read regardless their genre or author.