Above the Veil (Seventh Tower Series #4) Book

Above the Veil gets a little more exciting still than the other books, and continues some character development on Tal's part. Nix did pretty well in making him sympathetic but consistently still learning -- you want to give him a Gibbs Headslap (you'll know what I mean if you watch NCIS), but at the same time, you understand where he's coming from.

More interesting world building type stuff is going on in this book, too, and Nix's writing improves with each book.