The Art of Hitting .300
This baseball book is the bible on how to bat that all others are measured against. One reason is that stop motion photography is used to analyze a number of great hitters' swings. It is an fantastic example of how good visualization and information design can transform a written explanation into something much more powerful. It is out of print, but still relatively easy to get. The original price for this book was $30, but expect to pay $40-$120 for a copy in good condition now. I recommend this for both players looking to improve their swing and for graphic designers looking for inspiration.