Whether you're scanning a novel at a book store or checking the first few pages online, it's the beginning words (the hook) that are enticing. One of my favorite authors who inserts lots of zingers in his writing is Nelson DeMille. His opening lines always grab you.
Here are a few links to opening lines of popular novels. Is there a favorite you want to add?
Thriller First Lines
Opening Lines
Diagram of Famous Lines
Best Opening Lines
First Lines from Famous Novels