Starship Troopers is good, vintage Heinlein. Don't expect an action packed romp like what we saw in the film (in-fact, the film departed so far from the book they hardly deserve the same name). There is some good action, but the novel is very political, and explores the nuances of military hierarchy, imperialism, capital punishment, and other hot-button issues & ideologies that are still very relevant today.
Agreed. Starship Troopers is probably still my favourite Sci-Fi novel; brilliant, and inspired many other authors of the genre, similar to what Tolkien did for fantasy, IMO.
Actually, I just finished John Scalzi's Old Man's War and the other two books in that trilogy. It borrows heavily from Heinlein (which Scalzi acknowledges) and is a rather quick, easy read, but was actually quite good.