Speaking of the genre's history, while "Beautiful and Innocent" is a good source of general information on that topic, it doesn't go into much detail about esu and nuances of Nobuko Yoshiya's writing style and career. For this reason, I highly recommend Michiko Suzuki's "Becoming Modern Women: Love and female identity in prewar Japanese literature and culture". More specifically, it has a chapter dedicated to "Two Virgins in the Attic".
Thanks for the recs! Do you know if there's any demographic survey regarding yuri readers other than this one and dynasty's a few years ago? I've actually been wondering and serching for good data and research on yuri for a while. it'd also be great if we could reconduct the survey on dynasty, it was really interesting. I know about works relating the history of yuri but not so much about who reads it, a sort of sociology of yuri.