Well, that was a quick read. Life As We Knew It is definitely one of those books that you just keep plowing though. I liked it. It's intense, but not over-the-top (the author could have made it a whole lot worse), and it was believable (well, mostly, since I'm still skeptical about what sets the disaster in motion). It's not a cheerful book, but it's a hopeful book. And the narrator/journal keeper sounds like a teenager, in just the right way.
There's a lot you could talk about with this book and it's worth reading.