The Guardian's "re-reading" of Alain-Fournier's novel is by Tobias Hill and worth a look! 

This web site contains some wonderful images of Alain-Fournier, his world, and one of the woman named Yvonne, who may have inspired, well, you know ....

If you'd like to put together your own map, seeking out "the lost estate" you could start here.

Otherwise, the red box gives you an indication of the region.

Click on the image for a larger version in a new window.

And in case you're interested in film adaptations of this imagistic, poetic novel, here is Vincent Canby's 1969 NY Times review.