The plot moves really quickly, which kept the pacing of the book exactly how I like it: practically at breakneck speed. I finished Promised really quickly because I simply had to know how it all ended for Leon, Gaia and Mya. 
 There were a couple of things that bothered me about Promised. Parts of the story started to feel repetitive to me. For example, how Gaia kept going back through the wall into the Enclave when she really shouldn't. That was another problem for me: Gaia kept making foolish decisions and putting herself in danger. She didn't grow into the leader I thought she would, although she did set things right for the Enclave and the people of New Sylum in the end. 
 My other main concern with Promised was with Gaia and Leon's relationship. I hated that she sort of strung Leon along for so long. The relationship felt one-sided, with more of the commitment coming from Leon. I didn't understand her hesitance to fully commit to him, especially considering everything he had been through to be with her. I didn't like Gaia's lingering feelings towards Peter and Will. I wanted the love square to be dissolved more quickly than it was. Although, I was happy with the resolution of the love story. 
 I could not believe how things ended with regards to Gaia and her ability to have children. That really broke my heart for her. Especially considering her career centers around childbirth! I did like that the ending of the trilogy wasn't your typical rainbows and unicorns HEA, though. I liked that there was some loss, which led to character growth. I liked that things felt realistic, but not so bleak as, say, Mockingjay. 
 Overall, I would highly recommend the Birthmarked trilogy.