The Well of Loneliness (1928)
by Radclyffe Hall
Typically known as "the first lesbian novel," upon reading it I would have to say it's closer to being about transsexualism/gender dysphoria than it is straight forward "lesbianism." Loosely based on the life of the Author- The Well of Loneliness is a straight forward bildungsroman where the protagonist happens to be a woman, who is attracted to other women and "feels like" a man. There can be no doubt that the "novelty" of having a novel with a lgbt type protagonist overwhelms any picayune concerns about whether or not Hall is a progressive stylist of the novel in the manner of other mid 20s English female novelists (Virginia Woolf.)
I can see where first-wave gender theorists/women's studies types might see Hall's "Steven" character as a self hating lesbian who only thinks she wants to behave like a man, but a more inclusive perspective might take the position that Steven is gender dysphoric, a man trapped in a women's body. The Well of Loneliness is a good example of just how supple an art form the novel is for an outsider looking in. The "outsider" quality brings interest in the novelty of the character, her position as the daughter of an English aristocrat privileges her viewpoint, making her ultimate dream acceptance by her peers, rural English aristocrats.