Stones of Memory — Thomas A. Easton

Four generations ago, the world collapsed in an eco-catastrophe -- a collapse brought on by overpopulation, famine, plague, and war. . . .
Now Felix Webb and his family are struggling to rebuild the poisoned world they have inherited. Little do they know of the ancient evils that lurk just over their horizon, or of the wisdom of the dead awaiting their discovery in the local cemetery.
The memories of the dead are the key to mankind's tenuous existence and tentative recovery. Embodied in living headstones that contain the recollections of those who died before the eco-holocaust. But even the wisdom of the ancients' lore may not be enough to save them.