This review and others are posted at Inspiring Insomnia.
I enjoyed the first book in this series, The Girl of Fire and Thorns, and of course, I can't help but compare the sequel, The Crown of Embers, to it. It lacks a bit by comparison, and I think the biggest factor was the feeling of repetitiveness in CoE. For the first 50% of the book, Elisa escapes from one assassination attempt to another. I did enjoy the growth she's shown between the two books, and the strong, confident Queen we see in CoE is barely recognizable from the timid, girl in Girl of Fire and Thorns.
And I have to mention Hector... Hector, whom I adored in Girl, becomes whiny and manipulative in CoE. I think this personality switch was designed to show the depth of his feelings for Elisa, but it just didn't work for me. I hope to see a return of Hector's self-confidence in the final book of the trilogy.