For more on this topic, I highly recommend Andrew Taggart's writing and talks on the topic:
Derek Thompson's recent essay in the Atlantic also touches on similar themes:
Two essays that stand the test of time on this topic are from the 1930's:
In addition to this, Tash Walker did some interesting research as part of her firms shift to a 4-day workweek, which really started as an investigation of this deeper philosophical question.
If you are feeling ambitious, the original book by Josef Pieper can be found here. It's less than 100 pages and very readable: