A lot of people on this forum will swear by Gordon Winterfield and the Demons of Magick books. I have read demons of Magick and some other books published by The Gallery of Magick. They are simplified versions of ArsGoetia and other systems but to be honest, I believe they are over hyped. The books suck in my opinion but maybe it's just me. The only book I liked and it gave results to me was their Magical Cash Book.