Coben novels follow the same path: first 80 pages where we wonder when is the story begins, then a rising crescendo pending for 200 pages where the excitement reached its peak. The problem in "Without a word" is that the ending comes too early and not live up to the outstanding level of proposed just before. The last 100 pages are read without much conviction. Moreover, Coben has the bad habit to get into the often muddy extrapolations when he could replace them with elements of the far more interesting story. I do not even talk about the introduction of many characters in a short time, which, if not a good memory, requires us to constantly go back and forth to see who is who.
Of course, when you attack a police officer is usually for outstanding and at this level, I easily give it 9/10. It lacks more and improve his style to make everything perfect it.
Otherwise, I had a good time with this book was my first experience of reading a detective novel. I even bought later "Match Point" which I just finished.