I'm up to Shiloh. I used to have a computer game (DOS) that played Shiloh. It seemed to be fairly realistic, if simple, but was a good way to understand the terrain and troops involved. Johnston of course adopted a rather strange battle formation, I gather everyone wanted to be the next Napoleon, and he was late getting into position due to rain and then off into battle that morning, or it could have been worse for Grant.
I had not realized the Grant and Halleck problems. I'm also kind of marveling at the resiliency of the Confederacy in being able to assemble an army and go on the offensive in the west at that point after having lost much of Tennessee.