Here it is, in spoilers, just in case:
[spoiler]There’s this kid named Jess, who’s the middle kid in this big, poor, family, and is pretty much ignored by them. He likes to run and draw, but the only one who’ll support him in his drawing is his music teacher, Miss Edwards, who he sort of has a crush on. Everybody else teases him.
Anyway, just before fifth grade starts, this rich family moves in next door, and they have a girl his age, named Leslie, who’s a real tomboy. It turns out Leslie can run faster than anybody, faster than the boys, and even faster than Jess. She beats him in a race, and they become friends.
When they’re out exploring the woods behind their houses, they find this rope on a tree over a creek bed,and decide that that will be their “special place”. They decide that this land is the “Kingdom of Terabithia”, and that they’re the King and Queen. They build a treehouse there (a castle), and pretend to rule there. The only way to get to Terabithia is by using the Bridge to Terabithia, which is the rope swing.
Time passes, and they become even closer friends. Leslie is one of the few people who respects Jess’s drawings, and Jess is one of the few people who can deal with Leslie being a tomboy. They talk about all sorts of things, and Jess gets to know Leslie’s parents, who are novelists and liberal activists, and Jess comes to realize that there’s more to the world than just the conservative rural Virginia he’s used to.
Then one day, Miss Edwards takes Jess to the National Gallery of Art in Washington DC. He loves it, because finally he gets to see all the art he just dreamed about, and he decides he really can become a real artist. When he gets back, he wants to share that experience with Leslie, but finds out she died. She was on the rope swing, swinging to Terabithia, when she fell off and drowned in the creek.
Jess is devastated, and angry at Leslie for dying and leaving him. After going to a memorial service put on by her parents, he goes back to Terabithia, and, in a rage, destroys the paint and paper set that Leslie got him for Christmas.
The next day, he’s ashamed of himself. He goes back to Terabithia and builds a real bridge there, replacing the rope, and then he makes a wreath, and holds his own funeral for her there. Then, still feeling the need to do omore, and to share what Terabithia means with somebody else, he finds his little sister, who adores him, but who he’s ignored, the same way his parents and older siblings ignore him, and takes her there, crowning her the new queen of Terabithia.[/spoiler]