Power of the Heir's Passion by L. R. W. Lee is a sort of a prequel to the Andy Smithson series. I assure you that this is the most accurate description of afterlife available, for the world of Oomladee, not ours. It is subtitled A Novella; not quite a book but too long for a short story. And it's a ghost story from start to end.
In book 4 of the Andy Smithson series, Phoenix, Arizona, receives visitors from Oomladee for a change. Resurrection of the Phoenix's Grace by L. R. W. Lee sees the conflict crossing the magical border before Andy's Mom sends him back to Oomladee when the situation at home gets out of hand and way too dangerous.