Fan service is internet slang for what happens when, for better or for worse, an artist gives the people exactly what they want. Philip Pullman's brief, exquisite novel ONCE UPON A TIME IN THE NORTH (Knopf; 104 pages) is fan service at its best. North is set in the same quasi-Victorian alternative universe as Pullman's Golden Compass, where every human is accompanied by a talking-animal soul mate called a daemon. It's a prequel, the story of how a young and not-yet-grizzled Lee Scoresby, gunslinging aeronaut extraordinaire, and his rabbit daemon, Hester, first met up with armored polar bear Iorek Byrnison. Nobody writes dialogue for gunslingers like a Brit: "Damn, Hester," Scoresby says, "you don't hit a drunk man with a stick." And, of course, nobody anywhere writes dialogue for bears like Pullman.