Well, what can I say here, because it hasn't got much of a story. It is the diary of Johnnie Rico, a young man who joins the Mobile Infantry. We see how and why he signs up. We see his entire training in bootcamp Arthur Currie and his memories of school. especially the Morality and Philosophy classes. And all the other things he comes in contact with, his Officers training, and of course, his fights!
If you have seen the movie, forget about the movie. The book is entirely different from the movie.
Heinlein did a great job, he made the book pretty realistic sometimes, and how he lets Johnnie explain the chain of rank and his HMF-class are very nice (the chain of rank is sometimes pretty boring, but I didn't want to miss the parts about his HMF-class!)
My favorite parts are his memories of the HMF-class: in that class he learns the principles of ethics and how the government of the future works. In that class are theories, like Communism, Capitalism, Crime and the Law systems of today, torn apart! Sometimes its quite funny (I thought it was).
We get to know every piece of Rico's mind. Who he is and how he feels. Very nicely done Robert!
It's a good book for the genre, nothing like the movie.
Title: Starship Troopers