THE DARK TOWER III: THE WASTELANDS, by Stephen King, Donald M. Grant, publisher, 509 pages, $38 hardcover; Plume mass market paperback, 432 pages, $15.

In the Afterword of “Dark Tower I: The Gunslinger,” Stephen King estimated that it would take him roughly 300 years to complete the story he wanted to tell. Ten years and two sequels later, his prediction is considerably more optimistic.

Each of the “Dark Tower” books constitutes a segment of one long story King first conceived in college after reading Robert Browning’s narrative poem, “Childe Roland to the Dark Tower Came.”

In a recent interview, King said, “All this is about, in the end, is that poem about Childe Roland, who’s a knight, who comes to this dark tower. He asks this ageless stranger in the poem, `Where it it?’ and the stranger tells him but he lies. But eventually Childe Roland finds it anyway. That’s where the excitement should begin, I always felt, but Browning ends his poem there, just `Roland winds his horn and goes.’ I always wondered, `It’s so beautiful, but what then?’ This whole cycle is an effort to say, `What then?’ because that has come clear to me now.”

King may know, but he’s not ready to tell us just yet. “Dark Tower III: The Wastelands,” begins and ends with the abruptness of a chapter break. In this third installment, despite an opening synopsis, the plot reaches a level of complexity that should send devoted readers thumbing through the previous books in search of references. When the fourth book appears it probably will not contain even a token “Argument.”

“My feeling,” King said, “is that if you haven’t come along in the first three, you have no business picking up the fourth anyway. Forget it, you’re not going to know and the synopsis ain’t gonna help you!”

As “The Wastelands” opens, only a few months have passed since the final action of the previous book, “The Drawing of the Three.” Roland is training Susannah and Eddie Dean in the arts of being a gunslinger while he himself is plagued to the point of madness by a strange case of “double memory.” There was a boy. There wasn’t a boy! his inner voices rage, the boy in question being Jake Chambers, who died and lived and died again in “The Gunslinger.”

Eleven-year-old Jake, alive again in hometown New York, circa 1977, is in the midst of his own inner crisis; I died. No I didn’t. Did too. Did not.

Using parallel reality and non-linear time to good effect, King pushes these characters to the brink of madness before Jake is finally “reborn” into the gunslinger’s strange “world that has moved on,” bringing with him necessary talismans in the form of two dog-eared books. One is a collection of riddles, the other an unsettlingly prophetic children’s book titled, “Charlie the Choo-Choo.”

Hints, intuition and outright magic draw Roland and his White Company to the ruined city of Lud where degenerate rival factions wage hopeless warfare against one another, long since having forgotten the reasons. The most dangerous being in the city is not human, but Blain, a sentient bullet train gone insane.

Blain the Mono, Charlie’s dark half and genuine Hal on wheels, is the embodiment and outward manifestation of the evil technological spirits which lurk beneath the city. Roland and his friends recognize Blain as an important factor in their journey. Placated with a riddle contest, Blain agrees to carry them on their way. It is in his less-than-reassuring care that King leaves our heroes.

It has been 21 years since Roland’s creation and resonances of his world appeared as characters and themes in many of King’s other books, especially that of demonic nemesis Richard Fannin, the Ageless Stranger, whom King clearly identifies as being one and the same as Randall Flagg, the Walkin’ Dude of “The Stand.” The image of the Turtle reoccurs as well, King’s ubiquitous symbol of the slow process of good in the universe which balances Flagg’s more energetic evil.

Despite the length of this book (509 pages hardcover), little physical progress is made toward the Tower itself. King concentrates instead on developing characters and details which advance the story line and set the stage for further action; in short, “Wastelands” poses more questions than it answers. However, the “Dark Tower” series, taken as a whole, has developed into an engaging fantasy saga not lacking in drama, humor, and mythic elements. Though not entirely satisfying in itself, “Dark Tower III: The Wastelands,” is an enjoyable, necessary segment that whets the appetite for more.

Lynn Flewelling is a free-lance writer who resides in Bangor.