One of the best books available on the subject of
immigration between Canada and the United States
is Marcus Lee Hansen's The Mingling of the Canadian and American Peoples.
In this text Hansen gives a narrative of the history of
immigration between these two countries. Unfortunately,
this book has a rather old publication date and it shows not only in
Hansen's style but also in his interpretation.
I would love to see a new text published on this subject, but until
that happens I feel that more people should read this work so
that they can become familiar with this issue
of transnational history.