Out of context, Odd Girl Out is nothing to write home about: the plot is a basic love triangle, it's set in a fairly colorless (meaning both that there's not much description and also that every character is white) 1950s sorority setting, and the characters (especially Beth) are complex and authentic but not necessarily interesting enough to make up for the plot. The prose is insipid and overwrought, emotional far beyond the content--pulpy.
In context as a very early lesbian pulp romance first published in 1957, the first in a line of lesbian pulps by queer woman writer Ann Bannon that kicked off the genre, this book is great. While it fits the social mores of the 50s (there's no happy ending for our star-crossed odd girls), it's remarkably pro-lesbian in spite of that.
Amid steamy sex scenes and sorority-party drama, two girls affirm to each other that loving each other--women loving women--isn't wrong or dirty, even if society has made it illegal. There is some dialogue about how lesbianism is the result of perpetual immaturity and you need to love a man to grow up. However, at the same time, a prominent subplot about another sorority girl who is caught in bed with her boyfriend and kicked out of the sorority, and the college, for promiscuity parallels the danger Laura and Beth are in, and that parallel draws a moral equivalency between heterosexual and homosexual romances. There's some interesting commentary on masculinity and male power that hints at approving of political lesbianism. Or at least, the impossible helpless position men put women in makes loving each other, and not men, more understandable to the author.
This book also contains a scene I found jaw-droppingly bold: Laura, the lesbian, and Charlie, the straight man, who are in a love triangle with Beth, the bisexual woman, are in a car together. Charlie has insisted on giving Laura a ride home from class, and wants to know why Beth won't come back to him. Laura looks him in the eye and says, "She doesn't love you." And he's forced to confront the fact that this tiny, timid girl is his romantic rival, and she's defeated him before he even saw her as someone to worry about. I haven't seen anything like it in pop media, not even in 2019, and I found it terrifically satisfying.
Solid recommend if you're interested in queer history, or just like dramatic pulp fiction.