By the President's Commission. "With a special introduction by Harrison E. Salisbury and other material prepared by The New York Times," for this paperback edition from 1964, which is unabridged. I also enjoy this edition's cover photo, in which Kennedy seems to be pulling a "...really?" face at various theories about his murder.
If you've never read the WR, this is a great research copy, in quite good shape for its age: expected edgewear and page toning, but a very straight spine, snug pages with no marks or dog-ears.