It will come as no surprise that I absolutely devoured this book. Loved every single page of it.
SJM is excellent. I will read everything she ever writes. And this, being her only standalone novel to date, was such a delight! 
I adored this reimagining of Catwoman and Batwing -- Selina and Luke have my whole heart. Their story is action-packed, thrilling, full of mystery, deceit, and so much heart. 

Selina --
The perfect boss babe main character. This is her story, that's for sure. She's strong, dedicated to her cause, loyal to a fault, and loves with her whole being. 
Luke -- 
The tortured hero. He's conflicted, devoted to his loved ones and to Gotham, and slightly cocky -- which gets him into a bit more trouble than he's ready for at first. But man, we love him. 

As always, SJM's storytelling is masterful, original, compelling, and keeps you guessing at every turn. 
Epic. Nerdy. Perfect.

This was a really great book!!! It was dark, but a lot of the darkness was hinted at rather than explicit. It was faithful to the comics and get a new story. I really liked that she paired Selina and Luke Fox. I've never been a fan of Bruce and Selina (too toxic). But Maas's version of Luke and Selina worked really well because they had some core things in common that Bruce and Selina never really had.

I had a few minor complaints, such as there being a seemingly sudden shift in Selina's goals. I think maas was trying to draw out the suspense, but it came off as inconsistent. Also, Selina made a lot of powerful enemies, and it did make me worried for her future in Gotham. (To be clear, it wasn't a cliffhanger in that it was open for future issues; I just know comics, and the enemies she made are formidable).