Economics in One Lesson is a book written in 1946, less than 10 years after Keynes wrote his The General Theory of Employment, Interest and Money. It covers subjects like "The Broken Window Fallacy," "The Curse of Machinery," Spreading the Work Around," "Public Works," Taxes, Credit, Inflation, Tariffs and many more subjects.
I personally found this very enlightening, because it picks apart and explains the subject in great detail and in clear, simple language. For example, in the Broken Window, a miscreant breaks a window at a bakery shop. This is (incorrectly) lauded as "work for the glazier" (the person who makes and installs windows) and that money is now echoing through the local economy. What Hazlitt explains (and most other economics people missed) is that while the glazier got that money, The cobbler and the tailor lost income, because the baker was planning on purchasing a new suit or shoes before being forced to spend it with the glazier to repair the damage. Or, the baker could have purchased extra equipment or hired help to improve his production capacity. The point being, the money would have been spent no matter what, but it was wasted on repairing damage instead of improving the baker's life.
With similar aplomb, Hazlitt takes apart subjects like "machinery kicking people out of jobs." Granted, a textile machine will produce more cloth than several people, putting those people out of work. What you didn't see was all of the jobs created. Engineers to design the machines, workmen to build them, salesmen to sell them, technicians to repair and maintain them and so on. The people put out of a job by the machine then go and obtain more training, improving their skillset and possibly making them more valuable (and thus paid more) than they were before.
The language and terminology are quaint, with Hazlitt referring to radios frequently (televisions did not appear commercially until 8-10 years after the book was written). However, his points are clear, sharp and concise. If you want to talk economics, this is a great book for detailed knowledge, no matter if it's your 1st or 10th on the subject.