I'd appreciate any readings that go into more detail on the documents found, or discuss other research beyond individual testimonies.
I guess my qualms are that the Yoshida Seiji testimony seems to be confirmed as fabricated, and that a lot of the material I've found (e.g., the UN report via Vox) are derived from it. Obviously I don't want to read revisionist whitewashes, but I'd like to have what is confirmed laid out.
Not sure there is an "unbiased" book. There are different viewpoints on the issue, how it evolved and who was responsible. Many articles in newspapers, including Korean papers with English translation.
One good title, George Hicks. The Comfort Women: Japan's Brutal Regime of Enforced Prostitution in the Second World War. New York: W.W. Norton & Company, 1995. 303 pp. $25.00 (cloth), ISBN 978-0-393-03807-1.
Another that is controversial, C. Sarah Soh, Review: The Comfort Women: Sexual Violence and Postcolonial Memory in Korea and Japan, University of Chicago Press, 2008.