As a descendent of the Pennsylvania Dutch and practitioner of the folk magic associated with the heritage I suggest the book The Red Church or The Art of Pennsylvania Braucherei by C R Bilardi.
Please note this particular branch of the craft is heavy in high German and Christian ideals using the bible and prayer along with herbs and other root work to heal and protect. Though this practice has been in the US for over 200 years it came to the Americas via Germany and before that Sweden since it follows the same migratory path as the Amish religion. It has evolved over the years to include folk magic of all the areas that it has dwelled in including some Native American practices. The first settlers of the Amish religion in PA incorporated many of the native herbs for healing from the locals. Please also note that the most famous of the practices of this branch of the craft, the Hex Sign, is not just for show as many of the research may imply. Many of the Hex signs that are seen by the public eye at the current time are just folk art however the Hex Signs not in the public eye are the real deal. These are placed on the support beams and foundations of new or refurbished structures. If one whom practices the art of magic in any form constructs a hex sign they are infusing magical energy into it and therefore creating an actual usable magical item.