Multiverse Series by David Weber, Linda Evans, Joelle Presby

The Union of Arcana has expanded through the portals linking parallel universes for over a century and a half. In that time, its soldiers and sorcerers have laid claim to one uninhabited planet after another, all of them Earth, and in the process, the Union has become the most powerful, most wealthy civilization in all of human history... moreThe Union of Arcana has expanded through the portals linking parallel universes for over a century and a half. In that time, its soldiers and sorcerers have laid claim to one uninhabited planet after another, all of them Earth, and in the process, the Union has become the most powerful, most wealthy civilization in all of human history. But all of that is about to come to a screeching halt, for the Union's scouts have just discovered a new portal, and on its far side lies a shattering revelation. Arcana is not alone, after all. There is another human society, Sharona, which has also been exploring the Multiverse, and the first contact between them did not go well. Arcana is horrified by the alien weapons of its sudden opponents, weapons its sorcerers cannot explain or duplicate. Weapons based upon something called . . . science. But Sharona is equally horrified by Arcana's "magical" weapons. Neither side expected the confrontation. Both sides think the other fired first, and no one on either side understands the "technology" of the other. But as the initial disastrous contact snowballs into all-out warfare, both sides can agree on one thing. The portal which brought them together is Hell's Gate itself! less

It began with two men. They came from very different worlds—entirely different universes, in fact—one using sorcery and the other using mental powers and steam-age technology. They met in a virgin forest on a duplicate planet Earth. Neither side knows who shot first, but each blames the other, and it doesn't really matter, now, because war has begun. War between the universes is the last thing responsible leaders on either side want... moreIt began with two men. They came from very different worlds—entirely different universes, in fact—one using sorcery and the other using mental powers and steam-age technology. They met in a virgin forest on a duplicate planet Earth. Neither side knows who shot first, but each blames the other, and it doesn't really matter, now, because war has begun. War between the universes is the last thing responsible leaders on either side want. But the fury of their respective populations, xenophobic fear of the unknown, and cries for "justice" (or vengeance), are all driving both sides towards the brink. And unscrupulous, power-hungry men—and Arcana and Sharona alike—have agendas of their own. The fuse has been lit, and a war stretching across the universes, fought between dragons, spells, and crossbows and repeating rifles, machine guns, and artillery is erupting in white-hot rage and fury. Where it will end—and how—no one knows. less

Entry #3 in the popular Hell's Gate series by 28 times New York Times best-selling author David Weber and Joelle Presby.The war between magically-gifted Arcana and psionically talented Sharona continues to rage. The dragon-borne Arcanan assault across five universes has been halted at Fort Salby by a desperate defense, but at atrocious cost... moreEntry #3 in the popular Hell's Gate series by 28 times New York Times best-selling author David Weber and Joelle Presby.The war between magically-gifted Arcana and psionically talented Sharona continues to rage. The dragon-borne Arcanan assault across five universes has been halted at Fort Salby by a desperate defense, but at atrocious cost. One of those costs was the life of Crown Prince Janaki, heir to the newly created Sharonian Empire, who went knowingly to his death in the tradition expected of the House of Calirath. And another price will be the sacrifice of his younger sister, Grand Imperial Princess Andrin, now heir of Sharona, for the accords creating the Sharonian Empire require the marriage of the heir to the Crown to wed a Uromathian prince.  Andrin bears her family's Talent, the Glimpses, which show flashes of events yet to come. She knows the accords must be secured . . . and like her brother, she will pay any price, make any sacrifice for her duty to her people.  Sharona's soldiers dig in, facing the Arcanans in a tense standoff which cannot last long. Both sides continue rushing reinforcements towards the front, but how do armies fight wars when they can reach one another only through the portals which join the universes? And far, far behind the front, carried by dragons, a young Voice name Shaylar and her husband Jathmar hurtle deeper and deeper into Arcanan captivity, their only protection the fierce personal honor of the Andaran officer whose men massacred all of their companions in the horrendous misunderstanding which began the entire conflict. Men and women of honor on both sides must grapple with the terrible costs and deadly secrets of the spreading cataclysm, and in the shadows, those who will balk at neither treason nor murder drive the conspiracies which pour fuel into the furnace. The stakes are high and the pieces are in motion, but there are factors known not even to the conspirators and not even a Calirath can Glimpse the final outcome.The Hell's Gate Series:The Road to Hell Hell Hath No FuryHell's GateAbout the Hell's Gate series: "Magic and high tech collide in this exciting military SF novel from bestseller Weber . . . The authors treat both societies sympathetically and realistically, with human vices and virtues evenly distributed."–Publishers Weekly About the Honor Harrington series: “Weber combines realistic, engaging characters with intelligent technological projection and a deep understanding of military bureaucracy in this long-awaited Honor Harrington novel…Fans of this venerable space opera will rejoice to see Honor back in action.”–Publishers Weekly “. . .everything you could want in a heroine …. Excellent … plenty of action.”–Science Fiction Age “Brilliant! Brilliant! Brilliant!”–Anne McCaffrey “Compelling combat combined with engaging characters for a great space opera adventure.”–Locus “Weber combines realistic, engaging characters with intelligent technological projection . . . Fans of this venerable space opera will rejoice . . ."–Publishers Weekly less