It is nice to know that you speak from admitted ignorance of your subject. I thank you for your blundering honesty.
You begin by admitting that you never studied the subject (Grant's memoirs) mentioned by Carrol, and then you go on to expound on other subjects you are either too prejudiced to comprehend or you have studied very little. And these are only your own admissions, so I am not calling you ignorant since you unabashedly proclaim it. Why speak of a book at all if you haven't read it. Simply because you think you know what it is about already? What ever you think of Grant (or Thucydides, or Caesar, or Trotsky, to mention other generals who wrote well, but who I may disagree with politically) what difference does it make to the quality of what they write, what you think of their historical role? Because you hate their historical role does that mean there is nothing you can learn from their writings? Or are you the kind of philistine who wont read Celine or Jean Genet because of their politics? Or wont read Proust because he was a homosexual?
As for your historical judgments they show no consideration at all. But what should I expect of some one who will dismiss a literary work because of his political ideology. But from the way you write, I would suppose you would prefer Lee, Stonewall Jackson, and the spread of slavery. Since you make no real distinction between Lee and Grant, Jackson and Sherman, I can't really tell.
Let us suppose that "the north" did not "hold on to the south". Then the fight for slavery would have occurred across the continent as it occurred in Kansas before the civil war. British imperialism would have united with a stronger and internationally recognized southern Confederacy, supplying it with arms, and spreading slavery (probably under another name to spare British sensibilities ) into the Caribbean, and Central America. The cause of black freedom would have never been contemplated in the northern states except by a few radicals. There would have been no 13th and 14th and 15h Amendments.
It is also interesting that you take the southern revanchist Confederacy's view of Grant's administration. Every single administration from the period of the end of the Civil War to McKinley's administration was deeply corrupt, whether Democrat or Republican. The historical emphasis on the money grab of Grant's administration has always had more to do with his support of Reconstruction, and his actual attempts to make the Reconstruction constitution work. The complaints about corruption in the Grant administration are true. But in the succeeding administrations big business men bought and sold the whole country by buying senators and administration officials, at a scale that was truly stupendous. The Grant administration led the way here and that is about the only thing that we can say was unique about corruption in the Grant administration. After Grant the corruption simply became normalized. It became the normalized corruption of both legal and illegal capitalist rent seeking. But we only hear about the corruption of his administration because it is rapped up with the so called "corruption" of reconstruction; the corruption of actually bringing some freedom to blacks in the south. The obvious corruption of black power, which is always corruption from the point of view of white supremacists.
Yes, I am prejudiced. The drunken-sod Grant and the insane Sherman, for what they did during the U.S. civil war are two of the few military men I can actually support, and the U.S. Civil War was one of the few wars actually worth fighting in.