When I first encountered the OR at the University of Texas undergraduate library, back in the early 1980s, I was amazed at how much shelf space it required.
All one-hundred-twenty-eight volumes, including an index and an atlas. Sigh. Nowadays it’s nice to have it all available at home—via the Web.
It still takes some work to find what you want, and then there’s the inevitable caveats:
“As primary source material, the Official Records are, without question, the most complete and impartial documentation on the American Civil War. They provide a foundation for serious research into virtually any aspect of the war. On the other hand, no study of the American Civil War should rely exclusively on the Official Records. The accounts contained in the OR were not edited for accuracy, and due to space considerations, only excerpts of reports were often included. Researchers should thus verify the information found in these reports with other source material to gain as complete a picture of events as possible.”
Moreover, the OR is officer material. Which doesn’t make it wrong, but can make it biased. It’s always worth scouting out the same material in the pages of Confederate Veteran Magazine (the original issues, published from 1893 to 1932, not the contemporary SCV ones) and other primary sources such as diaries and letters. The privates did not always agree with their officers, and just because they were privates and limited to one patch of ground in a larger battle, did not always make them wrong. Lots of weighing and evaluating can be necessary. But the OR is the place to start.