This is 1 of my 2 most favorite fantasy romance series EVER! It's romance, which means happy ending...which is why I read the genre, but the world-building is just as good as anything in the non-romance fantasy/sci-fi genre. Nalini Singh is truly an amazing writer and one I read to learn from just as much as I read for the enjoyment.
Slave to Sensation is book 1 in the Psy/Changling series. It features cat shifter alpha, Lucas Hunter, and cardinal psy, Sasha Duncan. I loved that it wasn't inst-love right from the beginning. The build up was so sensual as Sasha slowly gives in to her emotions and Lucas slowly sees that the Psy CAN feel something. The scene with the cub and Sasha's boot will always be one of my favorites. Both characters are complex and strong which makes for a very satisfying love story. Add in the search for a serial killer and you can't help but devour every word.