This is reminsence written about 1889, by Pvt Olney, 3rd Iowa, which fought in Williams Brigade of Hurlbut's div at Shiloh. Olney gives a well written, colorful and detailed accounting of his own actions, and the things he personally saw. Then he goes on to give a more general description of events, and comments on commanders and their performance, as well as some of the available literature regarding Shiloh. Olney sees the Federal vigilance as lacking, and that just a few hours of notice of the oncoming Confederate horde would have given the federals enough time to organize their defense for a repulse.
I knocked it down to 4 stars because Olney recommends the accounts of William Preston Johnston and Don Carlos Buell as the best available. I think both of those, while very good primary sources, also are very self serving (Buell's to himself, and Johnston's to his father).