This piece which appeared on the New York Times a few weeks ago got me hooked: "They had it made", by David Brooks. This is just one click away from the full essay published on the online June issue of The Atlantic, "What makes us happy", by Joshua W. Shenk.
Go back in time and there's another article on the Grant Study which appeared in the 1990: "Men at 65: New Findings On Well-Being".
Further back and you discover this book by George Vaillant, "Adaptation to Life", which tells us the story of the Grant Study men when they were 47.
There is also two interviews to members of the Grant Study, Donald Cole and Ben Bradlee.
A final curiosity: there is no Wikipedia entry on the Grant study.