Why did the wife..? Spoilers
He hated her, hence I gather he was an awful husband.
So why did she kill another woman, to make it look like her husband was innocent?
Would she kill to keep a man who hates her, who has a Norman Bates complex, and is guilty of killing five women..?
The wife was beautiful and had her own money and work. No reason to keep psycho husband around, you know.
I also would have wished we would get some insight in why he hated his wife, why he killed, and why his wife loved him.
A couple of other suspects would also have been nice, since I love a whodunit.