Bought a World Book set at last year's Berkshire Hathaway meeting, for something like $650 including shipping. Awesome deal.
My kids (10, 8) earn "check marks" for each 20 minute chunk of time they spend reading it, which they can trade in for various goodies. Usually before they go to sleep
Edit: Also, they have used it for school projects. 2nd grader had projects on Poland, Neil Armstrong, and pygmy rattlesnakes this year. Very handy as an introduction to a wide variety of topics.
My kids (10, 8) earn "check marks" for each 20 minute chunk of time they spend reading it, which they can trade in for various goodies. Usually before they go to sleep
Edit: Also, they have used it for school projects. 2nd grader had projects on Poland, Neil Armstrong, and pygmy rattlesnakes this year. Very handy as an introduction to a wide variety of topics.