WE HAVE HERE two writers of the first rank, both Newbery winners, each with a new book out this spring. Each book deals with children of divorced parents who are spending the vacations with their fathers. This kind of coincidence is what writers worry about in the middle of the night (after they worry about revisions and galleys and the plot for the next book).

But we all know that it's what an author does with an idea that matters. E.L. Konigsburg and Betsy Byars have done remarkably different things--with equally successful results.

In Journey to an 800 Number E.L. Konigsburg introduces us to Maximilian Stubbs, a.k.a. Bo, or Max, and then steps back and lets Max tell his story. It seems that his mother has just married F. Hugo Malatesta the First and is off on her honeymoon, after sending Max to stay with his father, Woody, the camel keeper. It is, in fact, because of the camel (Ahmed) that his parents are divorced. (His mother would rather have had a dog--and a settled-down life.) Arriving in Smilax, Texas, in his new navy blue wool Fortnum school blazer, Max meets up with Woody (and Ahmed) and together they begin an odyssey of sorts.

Max has a penchant for the first-class life, preferring restaurants with white tablecloths to fast-food operations by the side of the road, but that is not the way things are with Woody. From Smilax they go to Dallas for the travel agent's convention (Ahmed is a feature at the Mideast Arlines booth), then on to the Tulsa State Fair, Oakes' Dude Ranch, and finally Las Vegas. And what an assortment of people they meet along the way: Sabrina, who collects freaks, and her convention-hopping mother; Mama Rosita from the taco stand; and Trina Rose, a famous singer who is "fat like a huge scoop of vanilla ice cream that's been at room temperature for a couple of hours."

If the secondary characters are good, the principals are even better. Woody, with his red bandana and black Pinocchio hat, never pries, rarely asks questions, yet is 100 percent involved. And as for Max--in the course of the book Max goes from being a junior grade snob to someone willing to give the world a chance. And despite his belief that "first class is something I was meant to get used to," Max learns that first class is where you find it. Journey to an 800 Number is a warm, funny, and definitely first-class book.

Betsy Byars, in The Animal, the Vegetable, & John D Jones, tells the story of two sisters, Clara and Deanie, who are off to the beach with their father, Sam, while their mother goes on a combination business and pleasure trip. (More pleasure than business, according to the clothes the girls saw her pack.) What Sam neglects to tell them, however, is that his friend Delores, who writes a "kind of Dear Abby column," and her son John D are spending their vacation with them.

It would be hard to say who is more appalled by this joint venture. Clara and Deanie, who bicker constantly--about food and cheerleading and even fleas--are united on one thing: to make John D as miserable as possible. For his part John D prides himself on the fact that he has never tried to be nice in his whole life; he sees himself "as an antidote to the world's new niceness." It stops just short of open warfare. The girls threaten to snoop in John D's suitcase, and they mimic his mother's admonitions. John D, in turn, labels them "The Animal" and "The Vegetable." Through it all the grown-ups work at a forced cheeriness. And the vacation plods relentlessly on. There are cook-outs, charades, and a dreadful day at an amusement park. Not until a tragedy is averted do the children find out that they like each other more than they realized, more than they ever intended.

It isn't what happens in The Animal, the Vegetable, & John D Jones that matters here, but rather how it happens. There is a realness about the incidents that takes our breath away. An accuracy that makes us flinch. Because of Byars' skill in presenting the workings of a family, we know these children; we have ridden in the car with them, been caught up in their conversations. They are all important to us. But it is John D--arrogant, proud, and terribly vulnerable, who makes us care the most. It is John D who violates his own first rule: "Don't care about anybody," and violates it with style.

The setting of the book is a summer cottage on Pipe Island, and I, for one, was bothered by the fact that Clara repeatedly swims alone in the ocean--in a place where there have already been three drownings that particular summer; where the currents are known to be tricky, and there is apparently no lifeguard. And the fact that Delores says, early on, "I know absolutely nothing about the ocean," doesn't help. It may be quibbling, but it tripped me up, interfering with the flow of an otherwise fine book.