Jack Sawyer is twelve.  His mother and he are on the run, being chased by his "uncle", a business partner of his late father.  His mother is running from death as well, in the form of cancer.  And as usual with this kind of desperate runs, they both catch up somehow.
Then Jack meets Speedy, an old blues-artist, who reveals to him that Jack is not like other people.  Well, we all are unique, but Jack is unique in quite another way, something to do with a parallel world, referred to by Speedy as "The Territories".  In that parallel world Jack's mother's twinner is on her death-bed as well.  Illness or poison, who will tell?  But whatever cause, her death could cause evil things to happen to both worlds, and Jack is the only one who can stop that.  So he has a choice: let the queen of the Territories, together with his mother, her twinner in this world, die, or go on a quest to the other side of the country to pick up and use a Talisman, of which nobody really knows what it is or how it works...

I loved it.  The book is written by two people with very different styles, but they did a great job in blending them in such a way that you don't really care who wrote what, because you hardly see the difference anyway.  And yet I think both lifted their level up to the best of the other.

The story is, like any other Fantasy, totally impossible, but while reading it you don't think of that.  Everything fits, everything is possible, the explanations are natural.  It could be happening to someone I know, and the evolution of the boy, from a 12-year old lost in a world he doesn't understand to a young mature child with a purpose, is logical.  In short, whether you like Fantasy or not, whether you like King or not, this one is in my humble opinion a recommended read.