It's not easy to find good material on game design.
Here are a few web pages that might be interesting.
Fundamentals of Game Design
This is the best book that I've found on game design.
It's available through the UVU Library's subscription to Safari Books
You can get to this book using the link above or by going to
www.uvu.edu/library and then
clicking on the eBOOKS image link on the right-hand side of the page
toward the bottom.
I Have no Words & I Must Design by Greg Costikyan.
http://www.costik.com/nowords.html 1994 version
http://www.rpg.net/oracle/essays/nowords.html 1994 version at another site
http://www.costik.com/nowords2002.pdf 2002 version
2002 version at another site
I really like what these articles say about game design, but in a few
places it uses words that are offensive to me and might be to you also.
The Art of Computer Game Design by Chris Crawford
This is an old (1982) book, but it's still useful.
Here's the URL:
This web site has many resources about game development, including game
400 Project, Rules Worth Breaking
Audio in GDC Vault
http://www.finitearts.com/400P/400project.htmSpreadsheet of rules