I took world mythology classes in college and was fascinated by the worlds these stories inhabited. I was, and still am, convinced that in many myths and legends there is a nugget of truth, some event that actually happened to prompt those stories. Anthropologists and archaeologists can dismiss them as fiction and inventive imagination all they want, or relegate them to religious superstition and/or cult activity, but when the same themes, imagery and motifs show up around the world across cultures, something's up. There's so much we don't know about our past and will probably never know. I prefer to keep an open mind rather than throwing out the baby with the bathwater.
That being said, I read Sign and the Seal back in the early 90s on my dad's recommendation. Whatever else people may say about him, GH is an excellent, compelling writer. From there, when Fingerprints came out I read it, then read the rest of GH's books as they came out up to Supernatural. (Still haven't read that one yet.)