I think Empire Of Storms is my favorite in the series so far in terms of characters and story. I loved getting to see Manon's story progress and it was kind of nice to see Dorian actually like...doing something. I also really loved Elide's journey with Lorcan. She's so scrappy and I love her so much. 
 That said, it does continue to be upsetting that in such a huge world people of color have been all but nonexistent. I was also disappointed that (spoiler for Queen of Shadows, not Empire of Storms)(view spoiler)[Chaol got completely cut out after becoming paralyzed. I realize the book was already quite long, but it was a missed opportunity. Especially since it seems likely he'll be magically cured before he returns, as if he couldn't contribute to the effort as a disabled character. (hide spoiler)] 
 Tl;Dr I loved the book but wish SJMaas would do more to diversify her casts. There's so much potential, but in a world this big the lack of diversity is not only problematic, it's downright unrealistic.