The Brandywine by Henry Seidel Canby.
Several years ago, on my first (and so far, only) visit to Delaware, I found this to be an enchanting small river. This historical study of the river makes a good read either before or after your introduction to the water rushing from Pennsylvania through Wilmington, Delaware to the larger Delaware River.
My only caution to the reader is to stay aware of the copyright date – 1941.
The shores of the river have been changed by man in these last decades. And while the river itself continues to wind through the land – the use of the land has changed from forest and scattered agriculture to sub-divisions and industry. (Not that industry is a new thing to the river. It’s water has powered many mills of many types through the years.)
History took place here. In the 18th and 19th centuries. And the 20th if you include the building boom which has taken place since publication. This book gave me a reminder that this nation is filled with moderate size rivers of great local importance.