Pendragon Universe

Bobby Pendragon is fourteen, has a basketball game that night and a girl he means to call, and instead his uncle Press pulls him into a flume that drops him on another world in the middle of its own worst decision. Halla is every territory and every time, all of them real, all of them happening. Saint Dane travels it too, and his method is never conquest: he finds the moment a world is deciding what it will become, and he pushes. D. J. MacHale wrote ten books of it, told half in Bobby's journals home to two friends who read them in a New Jersey basement. The territories are the pleasure — a water world, an underground city running on machines nobody understands any more, a game-show planet where the losers do not come back, and a future Earth that arrived there by a route the reader can see coming a long way off. The Travelers prequels hand the other Travelers their own beginnings. It is young-adult adventure with the pacing of a serial and a genuinely nasty villain who wins often enough to matter. Read them in order, beginning with The Merchant of Death; the journals build one continuous argument about whether people can be trusted with their own turning points. The prequels are for after you know how it comes out.