I like long, in-depth book reviews. I like reading them. I like writing them. I think they're helpful. That said, I don't have a lot to say about Cast in Ruin. I adore the Elantra series, and this book didn't disappoint. Also, at this point, if you're not reading the series, a review of the seventh book probably isn't going to entice you to pick it up and read it from the beginning.
I will say that one of the things I've found interesting about Sagara's plots for the last two books is that each book dramatically ups the stakes.
The strangers come from another world at the end of the last one, and this one introduces a female dragon who knows the Outcaste Dragon. I have read books where this leaves you excited for the next book only to have the next book do nothing with the change to the world. To Sagara's credit, this hasn't happened with the Elantra series. I'm excited to see what happens with the world in the next book, and I expect Sagara to provide me with an interesting answer.