Yes, historians estimate that at least 400 women managed to serve in the military during the Civil War. Some of them even left personal accounts behind! Sarah Rosetta Wakeman, who died of dysentery while serving in the union army, wrote a lot of letters home, which have been published. Sarah Edmonds Seelye wrote an autobiographical account of her time with the union army, titled Memoirs of a Soldier, Nurse, and Spy. Loreta Velázquez wrote The Woman in Battle about her time in the confederate army, though parts of it are considered suspect in terms of accuracy. If you're interested in hearing from some of the female soldiers themselves, I'd especially recommend Wakeman's letters, given they were exactly contemporary with and a direct reflection of her military experiences.