Dance of the Sun and Moon (2011)

From the front of the book:

The orbit of Toril’s moon often brings it across the sun's path, but astrological predictions of an upcoming total eclipse have sparked great interest. Many followers of Amaunator and Selûne have gathered at the small city of Sapra in the land of Turmish, the best place from which to view the eclipse. The worshippers of the Moonmaiden see this as a time of celebration, with their Lady ascendant, while those who revere the Sunlord are less enthusiastic about the celestial conjunction. But it is the followers of a different entity, guided by maddening whispers, who prepare to enact a far different ritual when the earth darkens and stars shine at midday. A Living Forgotten Realms adventure set in Westgate and Turmish for characters of the Heroic tier (levels 1-10).