Emperor Karl Cullinane, his son Jason, and his fellow Earth-exiles--Andrea, Ahira, Walter, and Lou--become the target of the evil Ahrmin of the Slaver's Guild in The Heir Apparent, while in The Warrior Lives, Jason Cullinane inherits a kingdom upon his father's death and a quest to rid the world of slavery, and must battle the mighty slavers guild while trying to discover the truth about his father, in an omnibus volume.
Librarian Note: There is more than one author in the Goodreads database with this name.
Note: This is a different person than the political/thriller author, Joel C. Rosenberg
Joel Rosenberg was the author of the bestselling Guardians of the Flame books as well as the D'Shai and Keepers of the Hidden Ways series. He made his home in Minneapolis, Minnesota.
Books 4 and 5 actually improve the series by focusing less on Karl and more on his son Jason. This makes the books more interesting as the adventures they get involved in seem more real somehow without having a warrior around that wins every fight by just busting in and chopping heads off.
The weariness of the characters start to show, the reality of life starts to catch up with some and all in all its a pretty quick fun read.