Not fair at all. I criticize Abraham Lincoln plenty, mainly for allowing the Democrats to establish governments in the seceded states before the war was even over.
Not fair? You are trying to make money, correct?
Since Abe is the first picture on your book, it's a fair assumption that buyers of it would at least have a passing admiration of him.
I will say that I have not read your book, so I do not know how much you did or did not criticize Lincoln.