Terry C. Johnston (RIP) prided himself on writing 'historically accurate' fiction in his 'Plainsmen' series. Yes, the main character, Seamus Donegan, is fictional but he's just a device to travel through the events as they actually happened, the events being the Indian Wars on the plains in the 1860s an 70s. 'Devil's Backbone' is the fifth book in the series and deals with the Modoc War.
We follow Donegan in his ongoing search for his uncle. The fact that the author tries to put as much history in the story as possible, definitely slows the book down. Whole pages and chapters read like a non-fiction history book (which it apparently is, at those instances). In the previous novels, fact and fiction seemed better integrated to me. As a novel, it didn't appeal to me as much as, for example, 'Sioux Dawn' or 'Red Cloud's Revenge'. Still, it's a fascinating period in history and 'Devil's Backbone' is definitely very informative.