What to read after Assault on Fort Bennett?

It is 1866 and Colonel Thomas Sykes, late of the Confederate Army, is in Milledgeville gaol, waiting to be hanged, but he is pardoned and freed from prison, on condition that he helps find and release the president's niece, who is being held by a band of comancheros. This task proves to be far from straightforward and the colonel finds himself out of his depth when he is called upon to help assemble a number of Gatling guns which have been stolen from the army. Colonel Sykes will soon find himself caught in the middle of a fierce battle between the comancheros on the one hand and a troop of US Cavalry on the other. Will he succeed in his mission?