One thing that confuses me though. I understand that Harry's body was kept alive and maintained by Mab and Demonreach, but why exactly did his soul go back to it? Did Uriel send him back? or did Mab and Demonreach force it back somehow?
EDIT (fixed error pointed out by Snaps At Fireflies)
Harry died and his spirit left his body. Apparently his spirit was kept on hold for 6 months, then someone decided to give his spirit a chance to go back as a ghost. After that, Uriel gave Harry a choice to work for him in the between, or to go on to what is next. Harry chose to go on, which turned out to be to return to his body, so apparently Uriel sent his spirit back to his body.
A more difficult question is why Harry's spirit was kept on hold for 6 months. I'm afraid the answer is that the story Jim wanted to tell required that everyone else be 6 months along past Harry's shooting and disappearance. I suppose we could say that Uriel wanted to give Harry some perspective, and Uriel thought that was best accomplished by waiting 6 months. Yeah, that's the ticket.