The Trickster’s Heart by Molly Tullis

Across the Greek world, Hermes is known as the trickster. After centuries, he’s leaned into the title and ignored the unfair reputation that comes with it.
Hercules, the mortal hero, has already gained a fearsome reputation of his own. When he needs help to finish his last labor and gain immortality, there’s only one god who will be able to help.
After one drunken night of mistaken identity, Hermes and Hercules realize they have to come together to travel to the Underworld—if their hearts will survive the process.