About the ending,I think that Verity planted that letter for Low to find out and torture her for the rest of her life with guilt. Firstly in the letter Verity clearly mentioned that Jeremy was reading an e-book that didn't belong to her and she saved her anger for later. Judging by her psychopathic obsession with Jeremy, it is obvious that Verity would feel extremely jealous if she finds out that Jeremy was reading someone else's book and didn't bother to read Verity's books when she desperately wanted him to read them. Later Jeremy confessed that it was him who secretly admired Lowen's books and he was the one who suggested her name to the editor. Hence this proves that Verity was secretly jealous of Lowen from the very beginning. She also anticipated the fact that maybe one day Lowen would take her place just the way she anticipated Chastin's death. It is her obsession with Jeremy to think like that. On top of that Jeremy's reaction when he found out the manuscript wasn't like as if he were seeing them for the second time. When he found Lowen making a mess by entering Verity's room and claiming that she's faking her injuries he ordered her to leave and that's when Lowen handed him the manuscript which makes it clear that it was the first time he was reading it and that's what made him furious enough to kill his wife. If he had known it before then he wouldn't have let Crew to be around Verity because he knows it's not safe.Hence Verity wanted Lowen to read the letter because she knows Lowen would never reveal about it to Jeremy as Lowen doesn't want Jeremy to suffer and thus this concludes that she would carry the guilt for the rest of her life alone.