What I most enjoyed were the works of Hieronymus Bosch, especially the depictions of Hell. One would be hard-pressed to find anything more imaginatively gruesome in the works of modern day horror masters like Clive Barker. I also fell in love with the engravings of Albrecht Durer.
Despite the fact that I am essentially non-religious, the rich symbolism of religious works from all cultures fascinates me, especially the interesting ways that they tend to connect across cultures; so this was an excellent book for someone like myself. I would recommend it to anyone with similar interests.