The new book I Love It When You Talk Retro: Hoochie Coochie, Double Whammy, Drop a Dime, and the Forgotten Origins of American Speech by Ralph Keyes about slang sounds (and looks) great. You can read an interview with Keyes here. One fun nugget from the interview:
I was surprised to find out that there were no “secret decoder rings.”
There were secret decoder pins, but no rings.