I'm thinking of adding the Grand Prix to my openings. Does anyone have a suggestion for a good book to study to learn the ideas / strategies for the Grand Prix?

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schiller's standard chess openings has a quick intro to the ideas, with an illustrative game (anand-gelfand, 1996), but i don't know of anything in depth. 

Try Starting Out: The Grand Prix Attack by Gawain Jones.  It is a starting out book so it will have a lot of prose explanations.

You could also get Chess Openings for White Explained, althoguh that is a complete repertoire book and has about 50pages of Grand Prix stuff in it.  That would probably be better for memorization, I believe the Starting Out book would be better for you if you're just starting the play the opening.

There's a group, we play some vote chess, with discussion:

http://www.chess.com/groups/home/sicilian-grand-prix-attack