Hi Bruce and Martin,
This is a difficult area for English-speakers, as it is scarcely mentioned in English histories of the war. Indeed, it doesn't feature much in French histories either once you've left the Meuse region and St. Mihiel Salient.
As David says, from St. Mihiel the front left the River Meuse and turned northeast towards Pont-à Mousson. I'm afraid that I haven't got a really detailed map of the front beyond Pont-à-Mousson but roughly speaking it crossed the Moselle at Pont-à-Mousson before turning southeast and - again roughly speaking - following the valley of the River Meuthe to St. Dié. There it turned south to Colmar and southeast to the Swiss border. The Vosges is not my area, I'm afraid, but there are plenty of people on the Forum who know it well.
Here's a link to a map of Western Front that shows the eastern sector, although not in detail:
http://www.historyonthenet.com/WW1/westernfront.htmHere is a short overview and small map of the battle of Lorraine in August 1914:
http://timelines.com/1914/8/14/battle-of-lorraineThere is a nice description in English of sites between Pont-à-Mousson and St Dié here:
http://battlefieldseurope.co.uk/ww1fr.aspx I've used that one myself to find some out of the way places.
The area between St.Mihiel and Pont-à-Mousson is covered by quite a number of books written from the American standpoint. The Michelin Guide called The Americans in the Gt. War, Vol. 2, The Battle of St. Mihiel, covers it in enough detail for most purposes. I can give you some other suggestions in English or French if you are interested in more.
As to what to read on the area between the Moselle and the Vosges, as I say, I've never found anything in English covering that area but there may be others on the Forum who have. The Michelin Guides are still interesting, although they weren't all translated. If you read French try the following: Nancy et le Grand Couronné and Metz et la bataille de Morhange. There is another guide covering Colmar, Mulhouse and Schlestadt but despite being part of the series of battlefield guides produced after the war, it has almost nothing about the war in it.
The Lorraine front was pretty static after the first weeks of the war. Toul, Epinal and Belfort remained in French hands throughout the conflict as did Nancy, which was not a fortress city. The fighting to the north of Nancy in August 1914 on the semi-circle of hills called the Grand Couronné came within a few miles of the city but the hills remained in French hands and the Germans never came back. The views from up there are really astonishing in their extent.
The Americans did indeed take over part of the Lorraine front in 1917 and 1918. I know of no book dealing solely with their experiences in the area but it is mentioned in the relevant divisional histories.
There are plenty of interesting and forgotten places in the area - the Xon beacon, which has recently been cleared and has stunning views on a clear day, Ste Genevieve, which was smashed during the fighting in 1914 and has been rebuilt, Nomeny, where a large number of civilians were massacred (I think the figure is 72), Vitrimont, with a memorial chapel to almost 10 000 French dead, Lagarde, which was just inside the German border of the time, Baccarat and lots of other places.
I hope this starts you off. If you have other questions, just ask.
Christina