I read this because it is discussed in Janice Radway's Reading the Romance in the "Failed Romances" chapter. And I agree with Radway that it does fail as a romance, but I think that's because it's a romance intertwined with a morality tale and the morality tale dominates most of the book. Well, and because Rogers isn't the greatest writer.
Brandt, the hero of this book, is constantly thinking things like, "Sometimes... he wondered about everything—his whole way of life. Why did he bother? Always looking for new kicks, new women, new entertainment." or "what is everything about? The parties, the orgies, the constant search for new faces, new kicks—it was all getting stale and pointless" or "He [had been] only twenty. He felt as if he had done everything; there had to be something new to experience, some way to stop thinking." For most of the book, Brandt knows he has everything society says should make him happy, and he also knows he's miserable to the point of suicidal.
In a romance, the hero is saved by the heroine's love; in this book Brandt is saved by choosing to abandon his decadent lifestyle. He decides to settle down, get married (before a priest in a Catholic church, no less), embrace monogamy, and have children. Eve, the heroine, had been chasing "worldly success" and similar pleasures, but by the end of the book she, like the hero, realizes she has been hurting the people she should have loved and (implied) resolves to do better:
"Eve knew now that it must have hurt and confused her [mother] to have one of her daughters turn her back on all the values they'd tried to teach her. "Oh, Mom!" she thought suddenly, wretchedly aware that she'd even, at one time, been ashamed of her large, Catholic, middle-class family."
In contrast, the man Eve thinks she loves through much of the book, David, never questions his own selfishness, never recognizes how he is contributing to his own misery, and does nothing to try to redeem himself. From the git go, he doesn't love Eve, doesn't appreciate the good she does for him or his family, and and never intends to marry her. He also utterly fails to help his 17-year-old sister, who has begun pursuing masochistic sex because nothing else makes her feel alive or important.
When Eve tells him what danger his sister is in, David's more interested in hiding the family shame and protecting himself than in helping the vulnerable girl and ends up sending Eve into danger instead of doing anything himself. He is a complete hypocrite who scorns Eve for doing as he does, and who intends to marry a virginal girl who he can trust to be faithful to him while not in the least intending to be faithful to her.
In contrast, Brandt is anything but a hypocrite, and never shows any concern over the fact that Eve is promiscuous. Although Brandt initially takes advantage of David's masochistic sister out of sheer lethargy, while scolding himself for "giving her what she wants," in the end he sends her off with a psychiatrist "who specializes in disturbed adolescents," and who he believes will actually help her. He also recognizes what Eve has done for David's family and her other good qualities, making it clear that she is as worthy of marriage as he is.
I think the reader is supposed to believe that Brandt, while deeply damaged by his upbringing, is now trying to become a caring person and has taken some major steps in the right direction and will ultimately succeed. I don't think Rogers does a good job of conveying this, but I believe that's the message she's trying to send.