Sweet Cry of Pleasure (The Olympians, 4) by Marie Medina
Ares thinks his life will be simpler now that his affair with Aphrodite is over. However, he didn't count on finding out that Alala, his constant companion and best friend, has been waiting a very long time for him to end things with the love goddess. Alala, goddess of the war cry, has loved Ares all her life but never told him. Even when Aphrodite wasn't around, there was always another woman in his bed. Now she's taken a chance and allowed her feelings to show. Ares quickly becomes confused by his desire for her and his fear of losing her completely, if he makes the wrong choices. When a rival appears on the scene, Ares has to do something to make up for how blind he's been, or risk losing the perfect companion the Fates gave him so long ago.