Thea Harrison's series Elder Races is one of my all time favorites though her novellas have always been a bit of a hit or miss for me. The Wicked was definitely a hit though, and I would totally classify it as one of my favorite novellas by her. 
 Olivia and Sebastian are both pretty great characters and I loved seeing them together. One of my favorite parts of the novellas is getting to see more of the world that Harrison has created and we definitely get to see that with both of their lives/backstories and how they interact with the rest of the world. The secondary characters were great as well; I loved seeing Phaedra again and would really like to see more of her in the future - maybe even a full length book or even a shorter story? And I also really enjoyed the character of Bailey and the way the rest of the group was presented and developed. The plot of the story was pretty good as well, I was able to guess part of the end pretty early on but I'm good at that sort of thing and actually love figuring everything out before the characters do. 
 Overall a really great novella by Thea Harrison and if you haven't read it yet then you really should.