The woman in the fifth

I am almost relieved to read the other reviews on this site of Douglas Kennedy's latest novel - I wondered if it was just me who found the ending to this book rather pointless and bizarre.
I have read lots of Douglas Kennedy's novels and loved them all, as others on this site state they are always really insightful, show a great depth of understanding of his characters and always follow a really strong storyline. I was really excited to begin The Woman In The Fifth, the dust jacket of the book outlines a plot that sounds really promising as an American college professor trying to escape his complicated life in Ohio moves to Paris to begin again and meets a Hungarian woman there who he begins a relationship with.
To be fair at the start of the book it begins really well, Kennedy builds his characters well and I was really enjoying the book. The last 8 or 9 chapters however are almost like they come from a totally different book, suddenly we go from a novel about the observations of life and our characters in Paris, to one about some woman who is a figment of the main characters imagination (or not - I'm still not sure) who's been dead for years and who goes around murdering people who have done the main character wrong.
I probably would chance reading another Douglas Kennedy novel again but another one like this and I think it would be my last!