I went and bought some torches figuring that THIS would be how I could explore dark areas which block magic, but it turns out that torches are considered magic as well! What are other means of light? Also, I found one area under Sorpigal in which I could cast magic, but the Light spell did not illuminate the darkness. Yet another area where Light had to be recast each square...

Try Lasting Light. If it works like in MM2, you might be able to stack multiple Lasting Light spells before entering the dark area.

Won't have that until another 2 levels. Not so sure if that will work though. Manual talks about something called "Light factors" and says you can cast Light multiple times to accumulate them, while stating that Last Light gives you 20 light factors. ... but for example the halls behind the jail, no matter how many times I cast Light in a row a single step in any direction turns it to darkness.

I think that some areas are designed to be dark no matter what you do. In these places you are supposed to feel your way through, bumping into walls and mapping out the area yourself. Sometimes you can cast light to get a quick view but it will extinguish as soon as you move, so it's only to be used when you've gotten really disoriented and need to see where you are for a second.

There are other places in the game where the light spell will last for a while. But in these "magical darkness" areas you basically have to wander in the dark.

So yeah, Lasting Light seems to work if cast before entering one of these areas. "Stacking" light doesn't do anything, despite what the manual says. Casting 20 Light spells will not give you 20 'light factors' and thus Lasting Light... but Lasting Light will... last.

I could have sworn that stacking Light spells did work, for all that it's terribly inefficient. You weren't casting Light while in the dark area, were you? If you were, then you'd be getting no net gain since the +1 Light from casting the spell is immediately cancelled by the -1 Light from ending the "turn" in an area that decreases Light.