This book is best for the 20-30 crowd of single women but could extend to older women who haven't acquired enough self-esteem, wisdom, and/or people-reading, to be secure being single. Really - 3.5*. It has a lot of good stuff, though there is definitely some info way off the mark. I'll start with the good and useful.
Birch advocates authenticity in pursuing a relationship. She tells the reader several times to can The Rules. She advocates interdependence (though she doesn't use that word) with the right person and dismisses dependence on anyone as an unhealthy behavior. She encourages a lot of self-assessment as far as determining what you want. She introduces two "trifectas" (commitment and connection), both of which are useful. I believe a lot more focus should have been put on shared values, but since there were entire sections I could have skipped altogether based on values (being careful not to drink too much, when to start having sex with a person you're dating, etc.), it's clear that we're operating on different fields. However, most of the world is on her page and will likely find her recommendations on these things helpful.
That aside, I like what she says about not settling, though I think she misunderstood Gottlieb's premise in her book about "settling for Mr. Not Good Enough". I believe Gottlieb was advocating not writing off men for paltry reasons...meaning that if your so-called "standards" are sky-high (Birch illustrates some of these standards/rules very well in her book - requiring that he always texting you first thing and last thing of the day, never making plans last-minute, etc.) and rigid, then you need to ease up. Writing off someone because their hair is the wrong color, or they drive the wrong car is not the same as writing off someone because they have a major character flaw.
Things I didn't care for too much:
Birch learned how to write via the internet, which is VERY apparent. The book is conversational, reads like a magazine article, and has several telltale signs of the writer who hasn't really studied language: misses subject/verb agreement (something commonly done in speaking but isn't for writing), has lots of fragmented writing that read like a text message, etc. The audience its intended for will likely embrace these things along with her language along the lines of "I want you to..." and "You are awesome! You are worth it..." I find these parts irritating. The entire point of the book is to self-evaluate and make your own decisions, so having the author constantly say, "I want you to..." grates. The constant reminder to the reader that the reader is awesome, and a great End Goal woman (EG) is equally irritating. I'm sure there are plenty of people who are terrible partners who have read this book, not to mention many who are pretty average.
How do all her readers qualify as "awesome"? This assumption feels unauthentic to me. If it is authentic, then the criterion for qualifying as awesome seems to be solely the reading of her book. I don't think she intended this, but the implication is a bit much. The only thing I really hated was on p96. "The love of a husband or wife isn't for the sake of the husband or wife, but for the sake of the self." To be fair, she's quoting Dr. Art Aron and his self-expansion model. Nevertheless, I nearly flung the book across the room. Love, by definition, is NOT about oneself.
All that said, I think there was a lot of great advice in her book, with sound, logical information. I'd definitely recommend it to 20s-30s women trying to figure out dating and men. Lots of great stuff - the best of it probably being Maslow's hierarchy of needs, which is referenced several times. A diagram of it is on p99.