Asgard's Conquerors — Brian Stableford

Asgard's not an easy world to get away from. Mike Rousseau only wants to take a vacation in his home system, but he's back before he has time to draw breath, and he's been drafted into the Space Force once again. His new mission is even more dangerous than the last one, the number of his enemies has increased vastly, and his friends haven't improved at all. By way of compensation, he has another chance to get closer to the mystery at Asgard's heart--but the inhabitants of the megaplanet's core are no longer content to sit quietly and wait to be found. They've discovered the outside universe, and are trying to decide what to do about it--but they have problems of their own. Only Rousseau can cross the boundaries between species, and offer each of the races a possible solution. Another great entry into an exciting SF series!