The Waste Lands (The Dark Tower, #3)

Part III of an epic saga. Roland and his companions, Eddie and Susannah Dean, find the Path of the Beam that will lead them to the Dark Tower. Along the way, Roland adds two new members to his ka-tet (a group united for a specific purpose). In the decaying city of Lud, they encounter new dangers, including a sentient train that has gone insane.