Reddit reviews Gay Berlin: Birthplace of a Modern Identity

There are some great books and articles on this subject. I think that you should avoid the 1950s onwards, because that would be like confirmation for Peterson fans.

For the gay identity that the books that I recommend are:

https://www.amazon.com/Gay-New-York-Culture-1890-1940/dp/0465026214/ref=sr_1_1?ie=UTF8&qid=1522048690&sr=8-1&keywords=gay+new+york
https://www.amazon.com/Gay-Berlin-Birthplace-Modern-Identity/product-reviews/0307473139/ref=cm_cr_dp_d_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar
https://www.amazon.com/Homintern-Culture-Liberated-Modern-World/dp/0300218036/ref=sr_1_1?ie=UTF8&qid=1522048869&sr=8-1&keywords=Homintern


A free source that is full of primary sources.
http://rictornorton.co.uk