Imitation in Death [J.D. Robb]

I already know I'm not going to have a lot to say about this one. It took me three days to read, but that's because real life got a little hectic about the time I started reading this book.
This is another one of these books that I don't remember at all. Even after finishing it, I can't remember reading it.
I found the imitation part interesting, but I don't think a serial killer would really copy another's M.O. and keep changing it. I can see a copy cat happening (they do, after all) but not one that changes who they are copying after each murder.