How we cite our quotes: (Preface if applicable, Paragraph)
Quote #1
No more is needed to show that the Steppenwolf lived a suicidal existence. But all the same I do not believe that he took his own life when, after paying all he owed but without a word of warning or farewell, he left our town one day and vanished. (Preface 42)
The first hint of Harry's suicidal nature shows up early, in the preface, which is a glimpse of things to come. Later on the treatise will say that he's a suicidal dude, and Harry himself will tell us about his own suicide attempts.
Quote #2
But he has not killed himself, for a glimmer of belief still tells him that he is to drink this frightful suffering in his heart to the dregs, and that it is of this suffering he must die. (Preface 44)
Here suffering is compared to a drink that will kill Harry… kind of like his alcoholism. He has to drink down his suffering just like he drinks down liquor. The narrator of the preface is convinced that Harry hasn't yet done the deed. Do you think he's still alive somewhere, wolfing it up?
Quote #3
What is peculiar to the suicide is that his ego, rightly or wrongly, is felt to be an extremely dangerous, dubious, and doomed germ of nature; that he is always in his own eyes exposed to an extraordinary risk, as though he stood with the slightest foothold on the peak of a crag whence a slight push from without or an instant's weakness from within suffices to precipitate him into the void. (39)
The treatise on the Steppenwolf compares the suicidal person to a germ in this metaphor; then it compares life, for the suicidal person, to standing on the edge of a cliff. Both images convey extreme vulnerability or danger, even if from the outside it doesn't seem like the suicidal person is really doing anything out of the ordinary.