THEY CAME IN SHIPS is comprehensive whether your ancestors came from Europe, Central or South America, Asia or Africa. Author John P. Colletta provides understanding for the myriad of sailing records available. I have found this to be an essential tool and purchased a copy for my genealogy library.
This is an incredible resource for genealogy buffs who are trying to claw their way over brick walls in relation to ancestors arrival by ship. I particularly liked the scenarios he presents and then showed how to glean more info from those same records.
He also helps those who do not find their ancestors in the National Archives.