Hell's Gate

Book 1 of the Multiverse series by David Weber and Linda Evans. They thought they knew how the universes worked THEY WERE WRONG! In the almost two centuries since the discovery of the first inter-universal portal, Arcana has explored scores of other worlds... all of them duplicates of their own. Multiple Earths, virgin planets with a twist, because the ''explorers'' already know where to find all of their vast, untapped natural resources. Worlds beyond worlds, effectively infinite living space and mineral wealth. And in all that time, they have never encountered another intelligent species. No cities, no vast empires, no civilizations, and no equivalent of their own dragons, gryphons, spells, and wizards. But all of that is about to change. It seems there's intelligent life elsewhere in the multiverse. Other human intelligent life, with terrifying new weapons and powers of the mind...and wizards who go by the strange title of ''scientist.''