Book One of The Magic Towers, a fantasy series I am writing. A synopsis:

Keith lives in a small, midwestern city. He and his friend Woody still like to play role-playing games while their friends have moved on to more serious pursuits. Then a new student named Dominic Putnam moves into his great-grandfather’s castle-like house across the street from Keith. Putnam Castle and the Putnam family hide many secrets, including the existence of a teleportal connection to another world.
 A mysterious woman gives Keith a teleportation device. The kids visit the castle and use the rock and Keith’s device, just playing games, but find themselves magically transported to a strange world. All eight kids wind up in the Kingdom of Pandoon, where they are scattered by the wizards of the Gold Tower. Some become slaves in the tower, some wind up in the neighboring Kingdom of Arcadia. Thus begins an adventure for all eight to survive, find each other, and get back home. Along the way they befriend elves, dwarves, wizards, and anthropomorphic animals, some of whom can talk. They must fight strange beasts and evil sorcerers to survive. And not least of all are the dragons, some good, some evil.
The kids’ arrival coincides with a strange time, the ending of a thousand-year prophecy and the return of dragons and goblins. There are four Magic Towers between the two kingdoms, where wizards have trained for a thousand years, but the Magic is all but gone now and the future uncertain.