harder time with book 3. Maybe it was new characters and storylines and what not, or maybe it was the whole storm power stuff and shards and all that had kind of been revealed by then, (kind of like the OP mentions with metallurgy in Mistborn 1) but i really struggled to get into book 3/4 in the same way.

I need to go back and give it another go, because Way of Kings was an incredible ride.