Links to sites featuring the books as PDF or DOI images of their original format:
War of the Rebellion Series
War of the Rebellion Series Home Page at Texas University
Full biblio: The War of the Rebellion: v.1-53 [serial no. 1-111] Formal reports, both Union and Confederate, of the first seizures of United States property in the southern states, and of all military operations in the field, with the correspondence, orders and returns relating specially thereto. 1880-1898. 111v.
See also (keyword "Official Records," with links to selected volumes).