Ghostopolis by Doug TenNapel

In a world where the living and the dead coexist, a young boy named Garth is accidentally transported to the afterlife by a ghost wrangler. As he navigates this spectral realm, Garth encounters a host of quirky and mysterious characters, including a skeletal horse and a ghostly grandfather. With the help of these newfound allies, he embarks on a thrilling adventure to find his way back to the land of the living, all while uncovering secrets about his own past and the true nature of the afterlife.