I read a great book about a girl whose boyfriend died in a taxi crash in new york, she spends weeks in her flat talking to her dead boyfriend, then eventually goes back to work, I think she works in a glamourous sales job. Her and her boyfriend were appartment hunting when he died, I think she is english and comes back to england to spend time with her family after the accident, another character in the book is someone who lives in the appartment above or below her in her building. What is the title and author of this book