This is definitely the dictionary to read. Here's the link to Amazon. It's the New American Dictionary of Cultural Literacy and contains terms (sorted by discipline) that any truly literate American should know... stuff that comes up in everyday conversation and shouldn't make you confused. From Latin terms to American politics to a Biblical overview. From World history to famous book/art references to the physical sciences, this book has it all. And of course, there the listing of common idioms and proverbs. Nothing is oblique or seems too obscure for the layman but it's all terms that come up in the media ("embryonic stem cell" is included, for example but "CHO cell" is not.) Well worth reading and memorizing. I was able to get almost all of the ones in the Life Sciences and Physical Sciences sections but in the American Politics section, I was floundering.
Valuable procrastination... but then again "Procrastination is the thief of time".
--C.