[Update: the incomparable Languagehat found the answer: the book is Что непонятно у классиков, или Энциклопедия русского быта XIX века (What's Unclear in the Classics, or An Encyclopedia of Daily Life in Nineteenth-Century-Russia) by Iurii Fedosiuk. Fedosiuk called for such a book in 1959, but no one wanted to put the bell on the cat until he did himself. He finished it in 1989, but various difficulties prevented its publication until 1998, five years after the author's death. In 2012 the 12th edition came out.]
Several years ago I read about a book written to help Soviet-era Russian readers figure out the nineteenth-century realia they found in classic literature – things like how many desiatinas are in a hectare, or what counted as a lot of money to a middling noble family. I don’t think I ever had the book in my hands, but just by reading about it I learned the difference between silver rubles and paper rubles (ассигнации) that I’d skimmed over a thousand times without thinking about. Do any of you know what book this might have been? I can’t remember enough about it to find it online.