Through Stephen King’s long career, the Dark Tower has loomed in the background.

The Bangor author has followed his muse wherever it led, be it writing novels, short stories, nonfiction or screenplays, producing movies or TV programs, or even (God help us) making Hitchcockesque cameos as an actor.

Yet through it all, Roland of Gilead has hovered nearby, a ghost wanting to break through to King’s world.

At events for whatever current project he was promoting, King would be asked by fans when he would write the next book in the “Gunslinger” saga.

King visited Roland’s Mid-World sporadically while writing the first four books in the series; “The Gunslinger” in 1982, “The Drawing of the Three” in 1987, “The Waste Lands” in 1991 and “Wizard & Glass” in 1997.

King began writing the final three books in the “Dark Tower” series in 2001. If, as rumored, he’s wrapping up his career as a published novelist, it makes sense that he wanted to finish up the series that has become his epic.

“The Dark Tower V: Wolves of the Calla” hits store shelves tomorrow; “Song of Susannah” and “The Dark Tower” will be published next year.

As “Wolves” opens, Roland and the members of his ka-tet of gunslingers, the teen boy Jake Chambers, the couple Eddie Dean and Susannah Holmes and Jake’s pet Oy are continuing Roland’s quest to save The Dark Tower, the crumbling center of civilization in Mid-World. (Yes, The Dark Tower is much more than that, but there have been entire theses written on the topic. There’s not enough room here to cover its many aspects.)

Anyway, they get detoured to save a town in trouble (shades of “The Seven Samurai” or its offspring, “The Magnificent Seven”).

Calla Bryn Sturgis is an agricultural town in the shadow of the dark province of Thunderclap, beyond which lies the Dark Tower. The town has a plague that its residents don’t know how to eradicate.

Once a generation, a troop of invincible man-wolves rides forth from Thunderclap to steal one child from each of the town’s many sets of twins. Those that get returned are “roont,” becoming giants with the minds of children who live short lives and die horribly.

Most in town view this tragedy as the cost of doing business, figuring that losing some of their children is better than losing everything. A small group of townfolk disagree, and want to fight the Wolves, but aren’t sure how to proceed.

The town’s preacher, Pere Donald Callahan (formerly a character in the novel “Salem’s Lot”), mentions that there is a group of gunslingers coming through the region. (Callahan becomes a growing presence in this series.) A handful of residents eventually make contact, and recruit Roland and his friends to help them.

Much of “Wolves of the Calla” is taken up with the gunslingers’ preparation for the Wolves’ arrival. But they are also busy shuttling to 1970s-era New York City, as part of their quest to save The Dark Tower.

In addition, future obstacles and challenges are foreshadowed, hooking readers for the final two books.

For a 700-plus-page book, “Wolves of the Calla” moves along fairly briskly, with a multitude of subplots and characters for readers to juggle. In addition, King does a masterful job of weaving in Roland’s back story, enough so that even a “Dark Tower” novice can feel comfortable and would want to go back to read the previous four chapters in the series.

While every King fan has his favorite novel, “The Dark Tower” is King’s masterpiece, a sprawling Western set in a dying wasteland. “Wolves of the Calla” succeeds as a standalone work, but King also continues to weave his majestic tapestry while giving away maddeningly little.