I agree that the DELIRIUM issues are all great - especially the 1975-1979 book/compendium. Definitely a MUST HAVE.
I remember the SPAGHETTI NIGHTMARES authors catching a lot of shit back in the day; accused of making up some of the interviews(?!). Some of the interviewees claiming that they never spoke to the authors. I can't remember the official outcome other than lots of euro genre fans dismissing their copies.
Via obsessive cross referencing - the book 99 DONNE by Nocturno has an amazing english section in the back.
One of the most complete italian language giallo reference books I still use a lot is I COLORI DEL BUIO: IL CINEMA THRILLING ITALIANO DAL 1930 AL 1979 by Luca Rea.
Still, I also always find myself going back to Craig Ledbetter's still amazing GIALLO issue of ETC.