Forge of the High Mage
Ian C. Esslemont
When the fae king of Naenden returns home to his palace only to find that his human queen has committed treason by conspiring to assassinate him, he has the queen executed and decrees that once every mooncycle, he'll marry a human woman from the kingdom, only to execute her the following morning. Unlesss one woman offers herself as a sacrificial bride for the rest.