Poetic Violence

Scot is a teenager when he's hit in the head and wakes up able to see and hear human souls that remain on Earth. Many of these souls remain on Earth because they want justice against the murderers that killed them. They come to Scot seeking his help to achieve justice. Scot is haunted by a pretty, female, former FBI agent, named Sharon, who insists he help her catch her killer. Scot does so and they strike up a unique partnership.
Sharon helps Scot cheat gambling at cards in casinos. In turn, Sharon spies on killers, terrorists and human traffickers and gives Scot her Intel. Scot cooperates with certain state and federal law enforcement agencies along with the military to achieve justice and rescues victims. In this book, Scot confronts a scientist that has created a wormhole machine. Scot and Sharon get sucked through the wormhole to another world.
That world is some sort of science project created by the little grey aliens that visit Earth in saucer ships. The alien species, known as Greys, have used DNA from Earth and other worlds to bioengineer all kinds of different life forms on a very primitive planet. Monsters and humanoids of all types inhabit the planet, and Scot finds himself constantly chased with Sharon trying to keep him one step ahead of the dangers.
Scot meets and travels with a lot of very interesting characters.