It seems particularily powerful to me that Josef Čapek died in the concentration camp of Bergen-Belsen. One of the only voices we can hear of the millions silenced in those camp.

R.U.R. (Rossum's Universal Robots) was written in 1920, premiered in Prague early in 1921, was performed in New York in 1922, and published in English translation in 1923. Virtually every encyclopedia or textbook etymology of the word "robot" mentions the play R.U.R. Although the immediate worldwide success of the play immediately popularized the word (supplanting the earlier "automaton"), it was actually not Karel Capek but his brother Josef, also a respected Czech writer, who coined the word. The Czech word robota means "drudgery" or "servitude"; a robotnik is a peasant or serf. Although the term today conjures up images of clanking metal contraptions, Capek's Robots (always capitalized) are more accurately the product of what we would now call genetic engineering.
The translator (Paul Selver) changed the play quite a bit while preparing the English version, combining two Robot characters into one, and considerably toning down the ending. If you're interested in reading the play as it was originally presented to American audiences, read the 1920s version (most university libraries will have a copy -- it was tremendously popular in its day).
In the 1990s, a new translation, with much better dialogue and a chilling new final speech (new to English audiences, anyway) by the Robot Damon, was published in a Capek reader called Toward the Radical Center (with a short introduction by Arthur Miller).
[http://jerz.setonhill.edu/resources/RUR/]
Written just before WWII the Insect Play is a wonderful fantasy full of political allegory and social commentary. It is important to keep in mind when reading the Insect Play that Josef Capek died in a Nazi concentration camp.