I've always been especially interested in Civil War books published by local museums or historical societies. The hardcovers for these regional publications tend to be well made, the print runs rather low, though the quality of the material inside can sometimes be sketchy. Generally, the potential appeal to buyers is more localized than national. Every now and then however, you can hit a home run as to collectability and first-rate material. Local letters and diaries usualy fall into this type of category.
It appears that the Hudson, MI museum is now producing a volume like I've just described. It's titled Cleaning Up the Muss [sic] and is a small collection of letters from the surgeon of the 4th Michigan Infantry who I assume was from the area. A full on-line article can be found here. I've lived in Michigan for several years and have to admit I didn't know where Hudson is. It's located in the far SE corner of the state possibly closer to Toledo, OH than Detroit. The book is $20 softcover and $40 hardcover and can be obtained from the museum or library. Shipping costs are $2.50. Call (517) 448–8858 for more information. Proceeds from the book support the museum.