Two, if one counts Death of a Unicorn as well, in spite of its comedic elements.

I don’t think I’d even want it to be, to be honest. The original book was really just fascist apologia, and the later adaptations of it had the foresight to use that premise instead for more effective social commentary.

Edit: I should clarify that I don’t think Heinlein himself was a fascist, but Starship Troopers is easily read as such.

Ocarina of Time. Randomizer.