The book is Circe, by Madeline Miller.  

The story follows Circe, the banished witch daughter of Helios, as she hones her powers and interacts with famous mythological beings before a conflict with one of the most vengeful Olympians forces her to choose between the worlds of the gods and mortals.

“Circe” will surely delight readers new to the witch’s stories as it will many who remember her role in the Greek myths of their childhood... it engrosses and races along at a clip, eliciting excitement and emotion along the way. The novel’s feminist slant also appeals, offering... a reclamation of one of myth’s reviled women. Purists may be less enchanted, bemused by Miller’s sentimental leanings and her determination to make Circe into an ultimately likable, or at least forgivable, character. This narrative choice seems a taming, and hence a diminishment, of the character’s transgressive divine excess. - Claire Messud in New York Times