The story is very intriguing but at the same time could have given Jack from the previous life a little bit more importance but overall a great story. Keep up the good work.
Also, this is just me speaking from experience, but I spent 2 chapters on bringing Jack to his current position. Spending even half a chapter more makes the reader lose focus in the novel. And it has happened with one of my novels before which I had to drop for the exact reason. So I tried.