Cartomancy — Michael A. Stackpole

Under the shadow of invasion by a nameless enemy, there seems only one way to save Nalenyr from oblivion. The old heroes who once defended the land must be awakened. And accomplishing that requires a journey across the magical wasteland where they're rumored to be trapped -- a wasteland rife with magic and danger.

Grandson of the Royal Cartographer, Keles Anturasi finds himself trapped in an enemy nation where his skill may well be his death sentence. His brother Jorim is an ocean away, captive in an altered realm in which he's regarded as a god. And their sister Nirati resides in a paradise that exists between life and death with her insane grandfather and an ancient sorcerer bent on the world's destruction.

Now they and their companions must struggle to survive in a world where war on earth mirrors war in heaven. What the gods themselves fear, men must brave. Heroes and mystics they may be, but can any of them survive in a world where things are seldom what they seem: a place where dreams can become reality -- and reality can turn into a nightmare....