My kids learned (long ago) that if they ask me a question, they're likely to get a far more detailed answer than they expect. In fact, they developed the habit of appending "short answer" to their questions if they were in a hurry. What they don't realize is that their questions often provoke questions of my own. It was one of those "followup questions" that led me to discover the publications catalog of the Federal Reserve System. My son's question was answered by "Symbols on American Money" (available in PDF), but I wound up ordering about 15 of the Fed's publications in hardcopy. Take a look; there's stuff ranging from the comic-book "The Story of Banks" and the historical "Panic of 1907" to the meaty, 130-page "The Federal Reserve System: Purposes and Functions."