I really like PIECES! It was one of the first European cult films I ever watched.
It is not considered to be a giallo but it is not an exploitation/sleaze film either. I'd call it horror, slasher or whatever... Its not included in Blood & Black Lace and I agree with Johny that if you don't see a film in that book its probably not a giallo. However, I am sure that book is missing a few titles, not to mention it includes a couple that are not gialli: HITCH-HIKE for example.
I also need to watch that slasher film that Edmond Purdom (narrator in a few mondos) went on to direct after taking part in PIECES.