Just a word of warning - this first line discussion may have a few more spoilers than some of the previous ones. So if for some reason you have been dying to read Twilight but haven't gotten around to it yet, this post may not be for you. With that out of the way - on to the first line:
"I'd never given much thought to how I would die - though I'd had reason enough in the last few months - but even if I had, I would not have imagined it like this."
When you read this for the first time, without knowing where the story is actually going, there's no denying that this is an attention grabbing opener. In the first sentence we know that the narrator's life is in danger, death being the only likely outcome, and while the death she is actually facing is unexpected, death itself is not. What more can you want from a first line?
Oh, I don't know, maybe a first line that is logically consistent with the rest of the book? Yeah, that would be nice, but unfortunately we don't get that here. Let's break it down. So Bella is telling us that she hasn't given much thought to how she would die. This isn't surprising for a normal teenager, but I think it's pretty ridiculous to think that someone dating a vampire, hanging out with vampires, and being threatened by vampires (even the ones that are supposed to be her friends) wouldn't give a passing thought to how she might die. Maybe something like "It's not entirely unreasonable to think I might get eaten by a vampire"?
Clearly Bella/Meyer understand this, though, as the quote here immediately points out how ridiculous it is that Bella hasn't thought about dying considering she had "reason enough to." Okay, I'll give them the benefit of the doubt here. Bella was so in love with her super human boyfriend that she never envisioned how he, or any other vampire threat, could harm her, but she's now admitting that she should have at least considered the possibility.
"...but even if I had, I would not have imagined it like this." Wait, so you admit that you probably should have been considering how you might die since you are dating someone (and hanging out with others) who you would typically expect to murder humans and drink their blood, but now that you are contemplating how you might die you're surprised that you're about to be murdered by a vampire. Really? Really? How then, Bella, would you have expected to die? Some entirely non-vampire related sequence of events? That's like a death row inmate saying "I never put any thought to how I might die, but now that I'm in the process of being executed, I have to say this is pretty unexpected."
The thing that fascinates me so much about this opening line is how good it is the first time you read it, and how bad it is in hindsight. Without knowing where the plot goes you would never realize how ridiculous it is. In fact, if you are anything like me, by the time the flashback catches up to this part of the book and she's about to die, you will barely even remember that's where the novel started, let alone the exact phrasing that was used. I imagine that Meyer's only concern was getting the readers attention, inconsistencies be damned.
Note: This analysis makes it sound like I hated the book. I didn't - I just think the opener is laughably ridiculous.