I liked that this was set somewhere different (in this case Mongolia). I enjoyed Thalia and the fact that she was not TSTL. I loved that she was able to save herself at the end of the book. I would have liked to have had less staring/watching/looking between Thalia and Gabriel. I also thought Gabriel was too focused on how unconventional Thalia was. The first half of the book was a bit slow going. Once they found the Source it picked up. The end of the book packed a punch and made up for the slow beginning.