In truth, it was not Karel himself who coined the term "robot," but rather his brother Josef, an artist, illustrator and book designer. (The word robota in Czech literally means labor, or serf labor.)
Josef Čapek fell into designing book covers after World War I, using scrap linoleum instead of printing blocks due to the latter's high price. Since the books that were being printed were not expected to have a large print run, he didn't have to worry that the design cut into the linoleum would hold up.
Čapek had this to say about the usage of the material: "Linoleum panels radically dominate the whole printing area. They divide it and color it at the same time and do so boldly. Linear painting for printing blocks, by contrast, would rather seduce the artist into certain restrictions, more timid, and with a less comprehensive composition."
Čapek also viewed the book along with its cover as an individual organism with a personality all its own. He wanted to give each of his covers an "inner substance" specific to the work. "It is not the same creating a book cover for an author who writes with light elegance, as for an author whose writing is dark and dense.... The content and character of the book itself...elicit a range of images and associations for the creator of the book cover. It is essential to give these images the most simple, most pragmatic and clearest expression, entirely distinct from associations that are formal, colorful, emotional or dynamic."
Here's the cover for Továrna na Absolutno:
And the charming book summary in both English and Japanese:
The above designs and many others are collected in Čapek's Bookshelf: The Book Design of Josef Čapek, published in 2003 by P・I・E Books. P・I・E is a Japanese publisher, and though their website does have an English portal, it's not that easy to navigate. My guess is that the book is now out of print, so it may be difficult or impossible to get your hands on. I'm lucky enough to have access to a copy at the local library here in Niihama. I revisit the book from time to time to flip through its bright pages and wonder what the future of the world will really be like.