I would also like to suggest "The Little Encyclodedia of Geometric Dimensioning and Tolerancing" by William Tandler. The format makes it very easy to look up specific topics. I have the Y14.5 standard, Lowell Fosters and Bill Tandlers book and I use them all.
For more information on Bill Tandlers book go to http://www.multimetrics.com/
Bob Connors
Lawrence Berkeley National Lab