Read the first book a while ago, reading deadhouse gates right now. What are some things I might have forgotten that I should know about?

I am at the start of the whirlwind where fiddler is trying to meet up with coltaine.

I feel like there are things I might have forgotten about that if I knew would further my enjoyment/understanding.

I remember the majority of the plot for GOTM. But, for example, I forgot Apsalar was a host for the Shadow king until it was mentioned by Fiddler.