Agree with you about James McDonough's book. It flows very well and is easy to follow - an engaging read. It doesn't bog down in military details. Interesting brief anecdotes throughout too.Larry Daniel's "Shiloh, The Battle that changed the Civil War" & James McDonough's "Shiloh, In Hell Before Night" are two amazing books that I found have the best flow to them, and are easier to follow, in my opinon.
Tim Smith's "Conquer or Perish" is far better if you're looking for an in depth military study of the battle itself, especially on the 2nd day.
Can't go wrong with any of these, though!