What to say? What to say? I feel strong ambivalence here.
Things I loved: Elend. Vin lost fights from time to time (in contrast to The Well of Ascension, in which she uninterestingly won every single fight and saved everyone always). The fulfillment of Sazed's quest for truth in religion. Marsh's struggle against external control. The Lord Ruler being a good guy after all! (That's not a spoiler, by the way. That's just my opinion.) Oh yes, and of course . . . Elend.
Things that made me want to pull my hair out: Hemalurgy everywhere. Everyone hears voices.
Hemalurgy, like Allomancy and Feruchemy, is a sort of magic involving metals. In Hemalurgy, a first being's Allomantic or Feruchemical power is transferred to a second being through the use of a metal spike by (1) killing the first being with said spike and then (2) embedding said spike into said second being. This is the method through which Inquisitors are created. It turns out that some other beings introduced in Mistborn and The Well of Ascension were also created through Hemalurgy. So now let's get to why Hemalurgy annoyed me so much: It was everywhere, and it large quantities, it became a little unbelievable. Spikes through eyes. Spikes through hearts. Spikes through shoulders. Spikes to grant sentience. Spikes of various metals. Spikes, spikes, spikes, blah, blah blah. Too many spikes!
So it turns out that the power Vin released at the Well of Ascension is called Ruin. Ruin is a god-like entity whose only desire is to destroy. Preservation, Ruin's opposite, was holding Ruin captive at the Well until Vin released Ruin. Unfortunately, creating Ruin's cage used up a great deal of Preservation's power, so Preservation needs assistance to stop Ruin. Throughout The Hero of Ages, Vin and her team seek to stop Ruin from destroying the world.
Before I go further into my critique, I must first state for the record that, despite my issues with The Hero of Ages, Brandon Sanderson remains a genius in my opinion. But . . . too many concepts in the The Hero of Ages were repeated over and over and over again. I got a little bored. Begin loop: (1) There is lots of ash. (2) Vin seeks her destiny. (3) Someone is hearing voices. (4) Elend is trying to do the right thing. (5) There is more ash than there was before. (6) Someone is being stabbed by a spike. (7) Sazed is having a religious crisis. (8) The koloss are coming. Repeat loop. That about sums it up.
The ending was great. Sanderson has a knack for writing great endings. I'm a little mad at myself that I didn't predict the ending. There were clues. I like an author who gives enough clues but still manages to surprise me.
I may (or may not) revisit this review after I've had time to think some more about how it all wrapped up. For now, I think I'm a little disappointed. But I have to give this book a relatively high star rating just because it was inventive, and it did wrap up a beautiful trilogy. I enjoyed it. But I wanted it to be better.