Steel's Edge by Ilona Andrews

The Edge lies between worlds, on the border between the Broken, where people shop at Wal-Mart and magic is a fairy tale—and the Weird, where blueblood aristocrats rule, changelings roam, and the strength of your magic can change your destiny…
Charlotte de Ney is as noble as they come, a blueblood straight out of the Weird. But even though she possesses rare magical healing abilities, her life has brought her nothing but pain. After her marriage crumbles, she flees to the Edge to build a new home for herself. Until Richard Mar is brought to her for treatment, and Charlotte’s life is turned upside down once again.
Richard is a swordsman without peer, future head of his large and rambunctious Edger clan—and he’s on a clandestine quest to wipe out slavers trafficking humans in the Weird. So when his presence leads his very dangerous enemies to Charlotte, she vows to help Richard destroy them. The slavers’ operation, however, goes deeper than Richard knows, and even working together, Charlotte and Richard may not survive... From Goodreads.

I liked how this book also placed the characters from the previous books in quite important roles at the same time as there is a new main couple. Charlotte and Richard are perfect heroes going after the slavers. The young boys, now teenagers, George and Jack are back and they learn something about their past.
The only thing is that the main enemy from the last three books, the Spider and the Hand, is fixed in about half a page. I think there should have been a bit more about that.

This book qualifies for:
Goodreads Reading Challenge 2015
I love Library books 2015
Wacky Reading Challenges: Word Search 2015
Wacky Reading Challenges: Mini Challenge 2015
Rawk-A-Tiers: Scavenger Hunt
A Million More Pages: Scavenger 2015
A Million More Pages Hogwarts: Dragon Nursery
A Million More Pages Hogwarts: Hogwarts Scavenger Hunt
Wacky Reading Challenges: Character Names, A-Z