I'm late answering this query, but think it's worth mentioning that Kuhns's book on the Germans coming to America seems accurate, though broad in topic - not specifics for genealogists but an overview of the period. I just dipped into it here and there, but saw no indications he'd fictionalized or exaggerated. I have long German experience as well as years spent researching PA immigrant families (both Mennonites of Lancaster and others in Berks and Lehigh Counties), and I think Kuhns did a good 1901-style historical presentation. Occasionally he inserts a comment that shows a rare grasp of the situation, such as his remarks on religion in the Palatinate in the 1700s. So on the whole I'd trust him.