It's high fantasy so didn't completely expect Vin (nor Elend) to die at the end. A riveting read nonetheless.

Some unexpected twists and turns (Sazed being the hero of ages) and late reveals (nature and appearance of the Preservation power/ god) but also things that are kind of expected (once you know piercing somebody with a metal spike binds them to the Ruin power/ god you know Vin's earring is doing exactly that - although it's "revealed" only later).