I have a pretty terrible memory for books, particularly books I've already read (see: every book in the Song of Ice and Fire). However, I know for a fact that I read this when I was a kid, and either I stopped reading it at some point, or completely lost interest, or didn't understand most of it.
And that makes sense. I was probably 12 or 13 at the time. Civic duty, or even the right to vote, was a concept way too remote for me to read a few hundred pages about the virtue of citizen franchise.
Reading it now makes me realize why the movie is so laughable, and the book is respected among the scifi community. I can't speak to the quality of the political arguments in the book, but they're certainly interesting to read and ponder, particularly when most scifi I read is nowhere near as contemplative.
Also, holy hell, they captured the military mindset well.