Oh, hai! I read books, then I write down what I think of them.
I want to try and avoid the obvious with these posts, so while Rebecca is one of my perennial favourites it's not going to be today's pick. Instead, I hit my bookshelf and pulled out the books I love at random to check their first lines with surprising results: very few have an arresting opener. There are plenty which have an excellent first paragraph, but opening lines, not so much. I think that's more a reflection of the books I own than anything else.
Anyway, my choice, for a book whose first line makes you stop and want to know more: Unholy Ghosts by Stacia Kane. Although I'm not much of an Urban Fantasy reader, I picked it up because it was 99p and because I vaguely know Stacia through AbsoluteWrite. It turned out to be a proper one-more-chapter read which demanded I create an elastic lunch hour.
Had the man in front of her not already been dead, Chess probably would have tried to kill him.