Because of the length of the coastline of the United States, from the beginning American ordnance and engineers placed an emphasis on heavy artillery mounted in coastal defences. The Union army organised its 'Heavy Artillery' into separate regiments, uniformed and equipped differently. While the Field Artillery was assigned across the fighting fronts Heavy Artillery units served the big guns in the forts and the defences of Washington. The Confederates did not differentiate types of artillery and those that became known as Heavy Artillery did so through informal association rather than formal designation. This book details the development and usage of the big guns.
Phililp Katcher has written over 20 titles in the Men-at-Arms Series including the highly successful five-volume set on Armies of the American Civil War.
Pretty good overview of Civil War heavy artillery, covering the various types of cannons, the types of ammunition used, etc. However, a couple bits could have been better: the "Heavy Artillery Usage" section concentrated mostly on the 1862 siege of Fort Pulaski, without mentioning any other battle that used heavy artillery. The sections about Union and Confederate organization were mostly just listings of heavy artillery units.