One of the most useful resources that I’ve taken advantage of during the past 15 years is David Henderson’s Concise Encyclopedia of Economics (originally the Fortune Encyclopedia of Economics). Its entries are written in crystal-clear language and, together, they cover an impressively large range of topics.
The first edition remains online here; I just discovered that the second edition has just been published by Liberty Fund. I’ll order mine now. I encourage each of you to order a copy. It’s a genuine gem.