I love this series, I do. However, I found Opal to be a little hard to get into and on the slow side. Partially I think it was me because I just felt in a down state as I was trying to read this. It was still great and had a huge cliffhanger at the end that makes you want more.
Opal takes place right after Onyx. I really love how each book ties in the gems to each story. We have all our main characters back and they are running into danger to save a few people. Will they be able to save the people they love? Or will they fail?