I read this book in English in 2002 or 2003. The book had a black cover with some circular symbol in the center, I can't remember the shape that was in the symbol.
In the book, the witch tried to murder every living human on earth, by targeting people one by one. She was able to make a body disappear after the deed was done. That is why she could kill so many without getting caught.
I remember two examples. One guy was killed when he stayed in a library by himself at night. she found him, killed him, and made the body disappear.
Another woman was killed when she left her house late at night to grab a taxi and meet friends.
Later, she felt more powerful and confident so she targeted small groups as well.
In the end, the witch was caught because she did not know her current targets were being followed by police agents who saw her and captured her.