Without a doubt, one of the most requested Reference books is the "Old Farmer's Almanac." A great resource for farmer's and burgeoning astronomers. Jokes, riddles, handy tips, weather predictions, planting tips...all since the days of Benjamin Franklin are in the pages of this handy dandy book.
Did you know that you can get all of this now online?
Check out http://www.almanac.com/ for this and much more.