Pages 1-40: "what is existence? It seems like a crazy question, but I'm going to answer it"

  The introduction (pages 1-40), among other questions, takes great pains to establish the question this book is about: "what is existence?" This is what "Being" is, by the way: it's just the ordinary gerund "being", as in, "to be". (I suppose it's not technically a gerund; instead it's just the regular noun (sometimes called a "verbal noun" because it's related to a verb) you might find in the phrase "it has being" (meaning "it exists", like "it has color" to mean something is colored)) An unfortunate choice has been made in its stylization during translation, for somewhat-understandable reasons. This choice, alas, makes it seem like it might be a specialized word. But the introduction is clear about the question this book addresses. The book is not about what beings exist, or what it's like to exist as a specific thing, but an investigation of existence itself.

  page 8: the term "Dasein" is introduced (shortly after its first use). This is apparently (colloquial) German for "guy" (in the broadest sense). A large part of the subsequent book is Heidegger discussing what guys are like (although not necessarily "what it is like to be" a guy). (Interestingly, this is exactly opposite his stated plan to address existence itself, and not the existence of any particular type of thing.)

  page 40: contains the disconcerting detail that this book is the first two parts of a planned six-part series that was never completed, and part three was supposed to be "time and being". Which seems very pertinent.

  page 4: Heidegger attempts to dismiss various arguments that "what is existence?" is a useless or meaningless or unanswerable question. His dismissals are unconvincing. But, the arguments he is dismissing were unconvincing in the first place. And so, who wins this argument — and, indeed, whether or not the very premise of the book is nonsense — depends on if Heidegger can in fact say anything interesting about existence. It all hinges on this: can Heidegger answer the question "what is existence?"

Pages 41-438: Heidegger fails to answer the question.