This is a subject I've been looking into for a while, along with weapons used. So far I've found no book or article covering Shiloh exclusively. The article I've found that goes in depth is Fred Adolphus's famous article on Drab uniforms and it is brief. Also one of his recent articles covering uniforms in different regions has a lot of Louisiana uniforms that fit into the Shiloh period pretty well.
As for Confederate uniforms I've found there are several uniforms associated with the battle. For example the "Cresent Regiment" there is a yellow trimmed frock coat associated with the regiment from the period, and a blue shell jacket if I remember right. Arkansas Regiments would have been a mix of Little Rock Depot frock coats, citizen cloths from home, and early commutation style uniforms. Texas is well noted for the various uniforms, famously white uniforms. Tennessee, and other States I've not gotten into researching as of yet.
I have a long way to go before the Shiloh CWT shindig.