I went 3, no 4, no 3, no 4, no 3 on this. And I realised this was an example of one of the traits of introversion, to decide correctly so as not to feel guilt. "Guilt" is mentioned 22 times in this book.
What sucked me in to trying this book was in the intro: "Now that you're an adult, you might still feel a pang of guilt when you decline a dinner invitation in favor of a good book."
In fact, it doesn't even have to be a GOOD book, just a book! Or a magazine! Anything rather than having to (gasp) socialise. And if one doesn't really drink much alcohol, or "a glass of extroversion", than it does become a painfully long ordeal.
The first 2/3 was quite interesting. About one-third of the population are introverted, but the extroversion bias of North American society, especially the US, means that introversion becomes regarded as a defect or something to overcome, rather than just a temperament which in many ways is more desirable than its opposite. Society needs both temperaments and the spectrum between them. (But try telling that to the pharmaceutical companies making Paxil and Zoloft etc., who would love to label as all as having 'social anxiety disorder'. They are trying to create disease out of normal human nature. They could make twice as much money if they instead try to create a disease of extroverts and call it something like "pathologic social exhuberance disorder". :-) )
The last part lost my interest, as it degenerated into a self help type style, thereby somewhat contradicting the first parts of the book. Still, it was an interesting enough book. I never read these kinds of books, so that I managed to finish it says something.