Warning: Possible spoilers below:

Wizard and Glass is the fourth part of the Dark Tower series by Stephen King. In this, the most recent chapter in the Dark Tower saga, we find Roland, Sussana, Eddie, Jake & Oy still aboard Blaine, the suicidal train. They manage to escape prior to being smashed to bits and find themselves in the Kansas of The Stand, after everyone has died of Captain Trips.

Travelling along I-70, Roland tells his band the story of Susan, his first love, and Hambry. As a youth and apprentice gunslinger, Roland is sent along with two of his friends, Cuthbert and Alain, to the Outer Baronies to collect inventory for possible future conflicts with John Farson (the Good Man). What they find in Hambry is worse than they could have imagined and it is complicated by Roland's affair with Susan. Here they also find the 'glass ball', a sort of crystal ball that is but one piece of 'the Wizard's Rainbow'. Roland learns of the Dark Tower after gazing into the ball and determines from that point on, the Tower is his quest.

Roland and company continue along I-70 where they encounter a large castle similar to the one in The Wizard of Oz. Here they meet an old friend from Lud.

The quest for the Dark Tower will continue, according to King, sometime in the next year or so.