Sadie When She Died - Ed McBain

First published 1972; cover shown is the 1993 reprint by Mandarin Paperbacks (UK). Cover art by David Bull. 160p.

One of the best McBain 87th Precinct crime novels I've ever read, with great dialogue, three dimensional characters and an ending you'll never see coming.

Also, possibly the longest sentence in fictional history (p. 9):

While Fletcher was remembering Carella's name; and while the police photographer was doing his macabre little jig around the body, flashbulbs popping, death being recorded on Polaroid film for instant verification, pull, wait fifteen seconds, beep, rip, examine the picture to make sure the lady looks good in the rushes, or as good as any lady can look with her belly wide open and her intestines spilling onto a rug; and while two Homicide cops named Monoghan and Monroe beefed about being called away from their homes on a cold night in December, two weeks before Christmas; and while Detective Bert Kling was downstairs talking to the elevator operator and the doorman in an attempt to ascertain the exact hour Mr Gerard Fletcher had pulled up in a taxicab and entered the apartment building on Silvermine Oval and gone up in the elevator to find his once-beautiful wife, Sarah, spread amoeba-like in ugly death on the bedroom rug; while all this was happening, a laboratory technician named Marshall Davies was in the kitchen of the apartment, occupying himself with busy work while he waited for the Medical Examiner to pronounce the lady dead and state the probable cause (as if it took a genius to determine that someone had ripped her open with a switchblade knife), at which time Davies would go into the bedroom and with delicate care remove the knife protruding from the blood and slime of the lady's guts in an attempt to salvage some good latent prints from the handle of the murder weapon.

A monster - and a great scene setup.