In the 60s and 70s, Larry Niven wrote a succession of Known Space stories which are considered some of the classics of science fiction, combining interesting hard science with fast-paced adventure. Now, like a visit from a dear old friend, he has returned to this fictional universe, in a set of collaborations with Edward Lerner.  The new stories, with familiar characters, include: Fleet of Worlds; Juggler of Worlds; Destroyer of Worlds; and Betrayer of Worlds