This is a Fantasy fiction/Science Fiction book I read that my dad owned, was probably back in the mid 90's that I read it.
Two kids (I think they were brother and sister) were kidnapped and transported to another world, a world of magic (Medieval sort of setting, very war-like). There were also other people who could travel from the world of Magic, this planet, I don't remember the name of, and Earth, the planet of technology. The goal of the Magic planet was to open the gate to the third planet, which used both technology AND magic. I think I remember the magic world preparing for an invasion of Earth as well in order to gain access to this new third world. I don't recall it being religion-based, I think it was very science-based. The magicians I believe used magic as a form of science or something. Details are very vague.
I think the one who kidnapped the kids was from the Magic world, or maybe it was a mistake? I kinda remember there were 2 "parties" that the view followed as well.
I remember the kids having magical abilities, once they got to the magic planet at least. There were 3 types of magic, each one harder than the last. I don't remember the first two, probably like visualizing, then transforming, but the last was creation, which you created something out of nothing. The boy was good at doing that, and bad at the others. The adult person who was with them realized what he was doing and was stunned, because that's the difficult magic to use. He was pretty much making magic air bullets for their gun, and just kept reloading it.
Can anyone remember this series? I think it was a trilogy, but this was some 20 years or so ago that I read it.