Wolves of the Calla (WotC) is the fifth book of 'The Dark Tower' series by Stephen King.
WotC primarily takes place in the title village of Calla Bryn Sturgis. Our ka-tet are charged with defending the village from the attack of the Wolves, horse-riding, green-cloaked, stylized-wolf-masked invaders who appear every few years, to steal away twin children (which the village produces in the majority) The children are taken away to Thunderclap Mountain, where one returns normal and the other 'roont' - a condition which causes simple-mindedness, and agonising extreme physical growth at puberty. Some of the villagers have had enough, and charge the Gunslingers with ridding them of the menace in exchange for the means to continue their journey towards The Tower.
Without wishing to spoil the story for those who haven't read it, this installment of the series sees events which will unavoidably make the Constant Reader somewhat uncomfortable - the ka-tet spends more time apart within the village; Jake makes a friend of his own age; the treatment of some of the villagers by others can be a little disturbing; Roland's hard-ass image is mellowed somewhat by his dancing the Commala, and taking a lover (that makes two - remember Allie in Tull? For a deserted world in disorder, this gunslinger ain't lost the old magic!).
There are also a few appearances (Marvel Comics' Dr. Doom, Father Callahan from Salem's Lot, and others which I'll leave you to unearth) which cause even the most die-hard fan to stop and wonder if Stephen King is really doing the 'right thing' with the series (subjective I know - he can write what he likes, I guess...).
The final scenes are fantastic, with some great action. Don't be put off by negative comparisons with The Seven Samurai or The Magnificent Seven - King shouldn't be over criticised for doing what many others have done before.
The end of the book will leave some readers in the same mood as when they finished The Waste Lands - it's a bit of a cliffhanger, but worth it!
King introduces a load of new Dark Tower jargon - 'commala' and 'todash' being the two most common, and while I personally think he's forced them on the reader a lot harder than some of the others we've come to know and understand (ka, ka-tet, khef, etc), a re-read helps bed them in with the rest of the parlance.
If you're a die hard fan - read it.
If you kinda like the series - read it.
If you haven't read the first four books - do so, or it just won't make sense!