After reading this book, I've decided that What's Your Number? is a miracle of a movie, having achieved what is nigh impossible for book adaptations and actually making the story ten times better. It is one of the only reasons I've rated this book as high as I have.
But first, the good points (or what the book did do better than the movie):
1) The companywide layoff makes much more sense than the random firing. Not that I don't get what the movie was trying to do with that, but the fact that Delilah (not sure why the movie chose to steal another character's name from this book, but it doesn't really matter, so it's not a point of favor or criticism for either of them) has severance pay makes the idea that she's going weeks without worrying about looking for a job fit together a lot better.
2) One of the only things I could've done without in the movie is the "chase him down to confess your love" bit at the end, and though I didn't actually like the over-the-top public display in the book, either, I do appreciate the effort to avoid that, even if it does make more sense for Delilah to approach Colin after having rejected him than for him to continue after someone who already turned him down.
Okay, on to my list of complaints, starting with the nitpicky:
1) My book is just riddled with copy errors. I was tempted to break out a red pen to make fixes, and I never, ever write in my books.
2) First person, present tense just drives me insane.
Moving on to story criticisms:
3) The embarrassment humor in this is actually worse than the movie, in my opinion, so congratulations to them for dialing it back. I don't know why chick lit books feel the need to mimic romantic comedies on that (okay, I do know why), but it simply doesn't work in this format (I'd actually argue in either format, but I know some people do enjoy it). It is just much more humorous to see someone mindlessly run outside in their underwear than it is to be forced to imagine it.
3a). People dying? Also not funny, but more on that later.
4) As someone who watched the movie first, I of course spent the book rooting for Colin and Delilah, but if I were coming into it this book fresh, I don't know that I would. The movie made the wise decision to eliminate Michelle, who served little purpose but to tell Delilah she's crazy for doing this and to help her find a job at the end, which resulted not only in a more authentic, closer relationship between Delilah and Daisy, but in a much more developed relationship between Delilah and Colin. Because there is no one else to talk to, he serves as her guide through this journey. We actually get to know him and see them establish a rapport and a bond that gets you to believe in their romance when it happens. In the book, they speak a few times and spend a weekend together. Oh, and he has nice abs and legs.
5) Jake Adams from the movie was just a much better way to end Delilah's arc than Nate. While Jake is clearly an elitist snob, that's really all you can accuse him of in the movie. Nate, on the other hand, is a racist serial cheater, the classic rom-com "other guy" intended to make you root for the end couple. The trope may be tried and true, but it is tired at this point and especially in this story. If it's all about accepting who you are, then the relationship should end on that mature note: "You're a good person, you're just not good for me." And not that this is all important, but it makes the ultimate choice more romantic, more genuine, because they're not being chosen by default simply because the other person is awful.
Finally, on to my favorite section, my liberal ramblings:
6) Edward, Daisy's fiancé in the book, is Black and Jewish. This is awesome, or would be, except for the underlying sense of ickiness I got every time a character patted themselves on the back for being okay with this, the fact that Delilah's first question is regarding "that stereotype," and the classic insistence that Delilah and Daisy's mom is "not racist, but." Now, the fact that she tries to educate herself is great, I'm not taking anything away from that, and it does, thankfully, ebb off over time (except for the crosses, ugh), but I couldn't shake the feeling she's the type to turn Edward into her minority shield ("my son-in-law is Black/Jewish, so I can't be racist!"), and that absolutely irks me.
7) Once again, having gay representation in this book would be awesome. Except for diving instantly into the Bury Your Gays trope, and not only is there that death and that attempt to make that death funny, but then there's the only person of color on Delilah's list. I reiterate: people dying is not funny, and especially not when it's focused on communities that already have a higher mortality rate than average.
8) Mocking people with disabilities (the woman with the lisp) is not funny and had no place or purpose in this book.
9) It is Not Great to spread the idea that drug rehabilitation centers are bland, lifeless, unhelpful places staffed by people who don't even have enough expertise to recognize that someone is not actually detoxing, or that psychosis stemming from drug use is funny, because look, he thinks he's in the movie Titanic.
Ultimately, this is just an incredibly rare instance in which I'd say: "Watch the movie, don't read the book."