While I do have Kody Keplinger's debut book DUFF, I have yet to read it. I don't know what made me read Shut Out first, but I did and I really liked it. 
 I am not sure just how realistic a sex strike is, not to mention one amongst high school students, but it was an interesting premise. It took the idea of sex being a weapon in a whole different direction. In this book, sex was a weapon used to bring about change. Or at least that is how it started, but alas, 'the best-laid plans of mice and men often go awry'. The girls, who believe they are holding all the power, are in for a bit of a rude awakening. 
 What I really liked about this book was not the sex strike, but rather the dialogue that sex strike provoked amongst the kids involved. These were kids like any others and they assumed that they were all having sex, when they weren't. The sex strike brought about several interesting conversations and realizations among both the guys and girls. These were conversations really brought home the message of being true to yourself in all ways. 
 Shut Out was a good book and a very easy read. It's one of the few books out there that I have read recently that has a pretty decent characterization of high-school students, their attitudes, and dialogue.