Wolves of the Calla is the fifth book in Stephen King's Dark Tower series. It follows Roland, a gunslinger, on his quest to find the Dark Tower, the nexus of all universes. Roland and his ka-tet, think of a ka-tet as a group of people brought together by fate, have escaped Blaine, the automated and psychotic monorail with a death wish and are once again on the march towards the Dark Tower.
In this installment of the series Roland and his ka-tet encounter a quiet farming and ranching town in the Mid-World borderlands. The town, Calla Bryn Sturgis, has been terrorized over the decades by a strange army they call the Wolves; called so because theirs faces look like that of a wolf. The Wolves sweep in from the east every 20 or so years kidnapping one twin from every pair in the town. Devastating in a town like Calla Bryn Sturgis where nearly all children born are twins and a singleton is rare. The stolen twin is eventually returned but when found is bereft of any intelligence. The townspeople call them roont. The town has been powerless to stop the Wolves who posses superior weaponry - "light sticks" (yes, just like the Star Wars light saber) and "sneetches" (a nasty parody of the snitch from Harry Potter novels - imagine instead of cute flying wings on the snitch a set of whirling razors that can "explode a man") and are always able to find the children, no matter how well hidden.
Mid-World can best be described as a post-apocalyptic America where the towns are a mix of wild west frontier and left over technology from ages past. King describes it as a place that has "moved on" and even time does not pass at a constant rate. Take Andy for instance - a humanoid robot powered by atomics who spends his time telling fortunes and occasionally assisting like a farm hand for hire. It is speculated that he has been around for nearly 2000 years. Contrast that with the lack of any motorized vehicles and relatively little use of electricity and you have the makings of world just close enough to ours as to fool you for a spell.
It takes some time but eventually the town believes that Roland and his fellow gunslingers can help and offer their complete support in the defense of their town. A gunslinger can be likened to a cross between medieval knight and wild west Marshall; someone to whom honor is paramount only to his responsibility to help those in need. Roland is first approached by Pere Callahan, the preacher in town. Here King pulls a looper and draws Callahan right out of his book Salem's Lot. When I say draw, I mean that just as Roland drew his ka-tet from other worlds, King has drawn Callahan into the Dark Tower series. By doing so King more tightly ties his own stories into the Dark Tower universe. I would go so far as to say that the Dark Tower universe provides the ultimate background story for many of King's other novels. From the blatant inclusion of Callahan to the more subtle connection of "the man in black" used throughout King's novels.
The other half of the book focuses directly on the quest for the Dark Tower. We learn more about todash - how people move between worlds. Roland and company find themselves fading in and out of his world and the world of Jake's New York. They must protect a special rose which is the incarnation of the Dark Tower in Jake's world. The rose grows in a vacant lot owned by a man called Calvin Tower who is being pressured to sell out to a land development company. It is through Calvin learn that the company is a front for the Crimson King's agents in Jake's world.
Prior to releasing this volume Stephen King made the announcement that remaining Dark Tower novels were essentially complete. There would be three remaining volumes, Wolves of the Calla being the first, and the final two would be released in the beginning and end of 2004. This book feels like the beginning of the end of Roland's quest. We learn more about the connection between Roland's world and our world and of the battle between Order and Chaos. We also learn more about the "breakers" and Crimson King referenced in King's "Low Men in Yellow Coats" novel. Overall a great read and more than ample reason to read through his earlier works searching for more connections.