Book of Sorrows: Book 4 of A Dragon's Guide to Destiny
by C. M. Barrett
The four stars of the series—a dragon, a cat, and two humans—go to the land of Tamaras to investigate a series of earthquakes. They travel through layers of mystery and deceit to an underground world, where a dragon queen appears to hold total power. Here they discover that invisible forces control the populations both above and belowground through a mysterious force called The Book of Sorrows.