Stopped for a tour a couple of years ago...well worth the time...and picked up a copy of "Red River Campaign, Politics & Cotton in the Civil War" by Ludwell H. Johnson, Kent State University Press, 1993 (ISBN 0-87338-486-5)

It thoroughly covers the battles at Mansfield and Pleasant Hill, but more importantly the whole scope of the Red River Campaign from Arkansas to New Orleans with all the whys and wherefores pretty well explained.

This Spring we took a thorough tour of the Fort Jessup S.P.--and while not involved (directly) in the nearby battles, as a part of American History (Louisiana Purchase through Texas Annexation) it's also worth a stop if you're in the area.