I read R. U. R. a while back, and I wanted to read the other three plays in the book, but I didn't get around to it for quite a while. Silly, because they are pretty neat.
The Insect Play: an entomologist observes several different kinds of insects, who illustrate types of humanity. Butterflies are flirtatious Bright Young Things with just one thing on their minds; dung-beetles only think about gathering wealth, while crickets are all about family, and ants have a fascist war-machine going.
The Makropulos Case: a lovely singer captivates everyone she meets. Men all want her; women all want to be her, but she is incredibly cold and unfeeling. It's about mortality and the necessity of death.
The White Plague: a new illness, which looks like leprosy but only attacks those over fifty, is becoming an epidemic. No-one can escape, and it's always fatal. A young slum-clinic doctor develops a cure, but he will only give it to the poor; the powerful may only have it if they cease a run-up to a devastating war. It's a savage criticism of the fascist regimes Čapek saw destroying Europe.
Interesting plays all. Very worth reading. I'll be looking to read some of Čapek's other works sometime.