Telempath by Spider Robinson
Isham Stone, the world's second-best assassin, goes into the ruins of a city after the greatest killer of all time, Wendall Morgan Carlson. But Carlson is guarded by ghosts - beings from an ancient civilization that shared the Earth with humans for millions of years, and who have now declared war on the human race, all thanks to the man Isham has come to kill.
Time Travelers Strictly Cash by Spider Robinson
Human or otherwise, regardless of race, creed or dimension of origin, if you're looking for a good time in a place where the beer is always flowing, and the stories always out of this world, step up to the bar at Callahan's. There'll be tales - Oh, are there tales! Like the one about a loud-mouthed time traveler who capitalized on a rip in the space-time continuum; or the...