His Dark Materials is also a superb choice, but it's pretty mainstream, most people are aware of it. Poor ole Friedman isn't well known at all.
What I love about Coldfire is it has a tad of sci-fi in it too, not much, but like, the 'magic' on Erna, where it's set, it's not just Harry Potter 'it happens' magic, it's due to various forces on the planet sorta like the wind and tides we have here, but it's an energy that is influenced and formed by the minds in it, creating magic or even sentient creatures, affecting the evolution of creatures, etc.
Also, there are various religious ideas, good vs. evil debates etc etc.
And then, Gerald Tarrant is a bit like a vampire (who feeds on fear) and is the coolest dude ever.