Donald, I assure you, there are three volumes to The Sias Family in America. AB Sias stopped at our farm in northern Vermont in the early 50s as it was Charles S's homestead in the early 1800's. He was thrilled to learn that my mother was (is) a Sias descendant. He picked her brain and that of her grandmother and so we figure in Volume 3.
My parents have all three volumes. Unfortunately, I'm in the Middle East and won't have access to them until next summer (assuming we're still around then).
Anyway, libraries should have all three. I'm pretty certain that the New England Historical Genealogical Society in Boston has them.
As to whether there's the demand, you'll have to gauge that yourself. I would be interested in all three but not particularly in Volume 1 alone (though it has a fine section on Jean Seyes).