Leslie's book is excellent.

Peterson's is riddled with factual errors, plagerism and academic fraud.

In one instance, he edited the content of a letter written by Quantrill in order to change its meaning. (Page 15…"From Lawrence, Kansas, he wrote to his mother on July 30, 1859, that a friend and he were attacked by a band of jayhawkers on the banks of the Little Cottonwood River and robbed of their horses and all their possessions. Quantrill explained that he was 'hunting away from the camp about a mile and a half & hearing the firing hurried to camp in time to see my friend lying on the ground apparently dead but still breathing with difficulty—having been shot 3 times, his leg broke below the knee, shot in the thigh with 7 iron slugs & last shot through the body with an arrow.'")
In writing of the attack on Q and his companion by Indians, Peterson maintains the attack was carried out by jayhawkers, and continues thereafter to defend the historically discounted story of Quantrill exacting revenge, one by one, on them. He quotes a small portion of Quantrill’s account of the attack found in a July 30, 1859 letter to his mother, but edited out the parts indicating the attack was the work of Indians. The full account of the incident reads:
"I am now in Lawrence after having spent over $300 & many a day & night when I expected either to be killed or freeze to death & at last when nearly in the settlements to have my horse and all taken from me & a companion of mine shot in 3 different places & left for dead & all that saved my head was I was out hunting away from the camp about a mile and a half & hearing the firing hurried to camp in time to see the indians driving off our horses & my friend lying on the ground apparently dead but still breathing with difficulty—having been shot 3 times, his leg broke below the knee, shot in the thigh with 7 iron slugs & last shot through the body with an arrow which I first thought would kill him but he lives yet & if taken care of properly will be as well as ever in 6 or 8 weeks. I hardly know what to do at present nor where to go but in my next letter I will be able to tell you some more. I think my friend & myself will make government pay us for our losses by the Indians if possible when he gets well."
This is a blatant and deliberate altering of a quote to give it an entirely different meaning. Although Quantrill used the tale of jayhawkers killing his brother at the Little Cottonwood in order to gain acceptance from Missourians, nowhere in the letter is there mention of the Little Cottonwood River or of jayhawkers—they are fabrications on Peterson’s part. This is academic fraud.

He used a movie script as an uncredited reference. (Page 430.."Frank James surrendered to authorities soon after his brother’s death with the promise that he be allowed to bury his brother.")
He fails to cite a source. Jesse was killed on April 3, 1882, and was buried two days later, on April 5. Frank did not surrender until six months later, on October 5, 1882. Peterson’s failure to cite a source may be explained by this transcript of what Stacy Keach (portraying Frank James) said as he surrendered at the end of the 1980 movie, "The Long Riders": "My name is Frank James. I came here to turn myself in. Here’s my gun. I want something in return. I want to be able to bury my brother."

A page and a half of Tom Goodrich's "Black Flag: Guerrilla Warfare on the Western Border, 1861-1865" was reproduced word-for-word without permission from either Tom or his publisher.