Such Sweet Sorrow by Jenny Trout
Never was there a tale of more woe than this of Juliet and her Romeo...
But true love never dies. Though they're parted by the veil between the world of mortals and the land of the dead, Romeo believes he can restore Juliet to life, but he'll have to travel to the underworld with a thoroughly infuriating guide.
Hamlet, Prince of Denmark, may not have inherited his father's crown, but the murdered king left his son a much more important responsibility---a portal to the Afterjord, where the souls of the dead reside. When the determined Romeo asks for help traversing the treacherous Afterjord, Hamlet sees an opportunity for adventure and the chance to avenge his father's death.
In an underworld filled with leviathan monsters, ghoulish shades, fire giants, and fierce Valkyrie warriors, Hamlet and Romeo must battle their way through jealousy, despair, and their darkest fears to rescue the fair damsel. Yet finding Juliet is only the beginning, and the Afterjord doesn't surrender souls without a price...