There must be many errors of omission in this work, because the subject is too large to be treated of in two volumes in such way as to do justice to all the officers and men engaged. There were thousands of instances, during the rebellion, of individual, company, regimental and brigade deeds of heroism which deserve special mention and are not here alluded to. The troops engaged in them will have to look to the detailed reports of their individual commanders for the full history of those deeds.
Wikipedia: Twain created a unique marketing system designed to reach millions of veterans with a patriotic appeal just as Grant's death was being mourned. Ten thousand agents canvassed the North, following a script Twain had devised; many were themselves veterans who dressed in their old uniforms. They sold 350,000 two-volume sets at prices from $3.50 to $12 (depending on the binding). Each copy contained what looked like a handwritten note from Grant himself. In the end, Grant's widow Julia received about $450,000, suggesting a gross royalty before expenses of about 30%.