cubfan,
I would suggest starting with this one:
Better Spelling in 30 Minutes a Day , by Robert Emery and Harry Crosby.
http://www.amazon.com/Better-Spellin...4268265&sr=1-1
Sorry, that was irresistible.
Seriously, two I would recommend are:
The Rules of Professional Baseball, by Chris Jaksa and Rick Roder. (aka J/R)
http://www.rulesofbaseball.com/
Baseball Rule Differences, by Carl Childress. (aka BRD)
http://shop.officiating.com/x/product/brd2006
I would also suggest a mechanics manual such as the PBUC "red book" or the CCA manual.
JM