Research on Books and Authors

Trying to price these volumes, having difficulties due to personal correspondence of authors.  Have tried libraries, no responses, tried some auction houses, found price if books  but no signatures etc.  Have contacted The Military Historical Society  of Massachusetts, where John Codman Ropes is a very prominent figure, no responses.

If anyone has information that would help, as in where else can I research etc., I would appreciate it. Thanks and have a great day.  Yvonne