The Varayan Memoir Series by Rick Shelley

The Buffer Zone--that was what the seven kingdoms standing between mortal Earth and the realm of the immortal elves was called. When Gil Tyner planned to celebrate his 21st birthday with his parents, he didnt have any idea that he was about to spend not only his birthday but possibly the rest of his life in this zone. Original.

Gil was just another college student when his father died and left him an incredible inheritance. Destined to be both the hero of Varay and the heir to its crown, Gil stepped through the magical doorway where he received a cram course in the hazards of the Varayan buffer zone. But now he would need all his skill, luck and wizard and warrior allies to face a new menace.

Concludes the thrilling medieval fantasy trilogy. With the end of the universe fast approaching, newly made king of Varay, Gil Tyner, must brave the perils of post-Holocaust Earth and then go beyond Fairy to stand against the Great Earth Mother herself in a battle that will either destroy all existence--or bring a new beginning.